The Bulletin of The Korean Astronomical Society (천문학회보)
The Korean Astronomical Society (KAS)
- Semi Annual
- /
- 1226-2692(pISSN)
Domain
- Earth Science(Earth/Atmosphere/Marine/Astronomy) > Astronomy
Volume 37 Issue 1
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Kim, Min-Gyu;Matsumoto, T.;Lee, Hyung-Mok;Arai, T.;Battle, J.;Bock, J.;Brown, S.;Cooray, A.;Hristov, V.;Keating, B.;Korngut, P.;Lee, Dae-Hee;Levenson, L.R.;Lykke, K.;Mason, P.;Matsuura, S.;Nam, U.W.;Renbarger, T.;Smith, A.;Sullivan, I.;Wada, T.;Zemcov, M. 42
The First stars (Pop.III stars) in the universe are expected to be formed between the recombination era at z - 1100 and the most distant quasar (z - 8). They have never been directly detected due to its faintness so far, but can be observed as a background radiation at around 1${\mu}m$ which is called the Cosmic Near-Infrared Background (CNB). Main part of the CNB is thought to be redshifted Lyman-alpha from gas clouds surrounding the Pop.III stars. Until now, the COBE (COsmic Background Explorer) and the IRTS (Infrared Telescope in Space) observed excess emission over the background due to galaxies. To confirm the COBE and the IRTS results and pursue more observational evidences, we carried out the sounding rocket experiment named the Cosmic Infrared Background ExpeRiment (CIBER). The CIBER is successfully launched on July 10, 2010 at White Sands Missile Range, New Mexico, USA. It consists of three kinds of instruments. We report the results obtained by LRS (Low Resolution Spectrometer) which is developed to fill the uncovered spectrum around 1${\mu}m$ . LRS is a refractive telescope of 5.5 cm aperture with spectral resolution of 20 - 30 and wavelength coverage of 0.7 to 2.0${\mu}m$ . After subtracting foreground components (zodiacal light, integrated star light and diffuse galactic light) from the sky brightness of observed five fields, there remained significant residual emission (even for the lower limit case) consistent with the IRTS and the COBE results. In addition, there exists a clear gap at 0.7 - 0.8${\mu}m$ in the CNB spectrum over the background due to galaxies according to recent results (Matsuoka et al. 2011; Mattila et al. 2011). The origin of the excess emission could be ascribed to the Pop.III stars with its active era of z = 7 - 10. -
Jeon, Lee-Seul;Song, Yong-Jun;Go, Yu-Gyeong;Kim, Eun-Bin;Kim, Ji-Hui;Bae, Hyeon-Jin;Lee, So-Jeong;Heo, Hyeon-O 54
한국 젊은 천문우주과학자들의 모임(Korea Young Astronomers Meeting, KYAM)과 일본 젊은 천문우주과학자들의 모임(Japan Young Astronomers Meeting, JYAM)은 지난 2006년부터 한-일 젊은 천문우주과학자들의 모임(Korea-Japan Young Astronomers Meeting, KJYAM-JKYAM)을 개최하고 있다. 이 모임은 학문 후속 세대로서 활발히 연구를 진행하고 있는 한국과 일본의 젊은 천문우주과학자들 간의 관계를 유지, 강화하여, 천문학 및 우주과학분야에서 많은 교류를 해오고 있는 양 국의 관계를 더욱 발전시켜 나가는 것이 목적이다. 제1회 KJYAM은 2006년 한국 경주에서 열렸으며, 그 후 2008년 일본 교토, 2009년 한국 과천, 2010년 일본 도쿄에서 진행되었다. 그리고 2012년 2월, 제 5회 KJYAM이 한국 연세대학교에서 2박 3일에 걸쳐 개최되었다. 이번 KJYAM에서는 일본 소속 1명의 SOC를 포함한 3명의 SOC와 1명의 초청 연사로부터 초청 강연이 있었고, 일본 소속 11명, 한국 소속 35명, 그리고 중국 소속 1명의 참석자들이 자신의 연구 성과를 발표하였다. 또한 경복궁 방문과 연세 KVN 전파망원경 견학을 통하여 한국의 오래된 고궁에서부터 가장 최신의 천문 시설까지 관람하는 기회를 가질 수 있었다. KYAM과 JYAM 두 모임은 이러한 KJYAM-JKYAM 모임을 지속함으로써, 양 국 젊은 천문우주과학자들의 친목 관계를 증진시킬 뿐만 아니라, 상호간의 공동연구 진행에 긍정적인 영향을 끼칠 것으로 기대하고 있다. 다음 JKYAM은 2013년 일본에서 개최될 예정이다. -
Kim, Yong-Gi;Yoon, Joh-Na;Andronov, Ivan L.;Breus, Vitalii V.;Dubovsky, P.;Chinarova, Lidia L.;Han, Won-Yong 59
Self-consistent mathematical model of the exotic object OTJ 071126+440405= CSS 081231:071126+440405 is discussed. The system was discovered as a polar at the New year night 31.12.2008/01.01.2009 by D.Denisenko (VSNET Circ), and we have initiated an international campaign of photometric and polarimetric observations of this object (totally -80 runs in Ukraine, Korea, Slovakia, Finland, USA) as a part of the "Inter-Longitude Astronomy" (ILA) project on monitoring of variable stars of different classes (Andronov et al., 2003). Here we present the geometrical and physical model of the system in the low luminosity state and in the intermediate luminosity state as well as in the high luminosity state. As the system is of -20 mag at minimum, no spectral observations were made to determine parameters of the red dwarf. From the statistical relationship, the mass of the red dwarf is estimated to be -0.165 solar masses, for the white dwarf (from eclipse duration) - from 0.5 to 1.76 solar masses. As the system resembles ER UMa in some characteristics, the lower value may be assumed. The inclination of the system and other physical parameters are estimated. The object is an excellent laboratory to study multiple physical processes in the magnetic systems. -
Park, Yeong-Sik;Lee, Dae-Hui;Jeong, Ung-Seop;Mun, Bong-Gon;Lee, Deok-Haeng;Pyo, Jeong-Hyeon;Park, Gwi-Jong;Park, Seong-Jun;Nam, Uk-Won;Lee, Chang-Hui;Park, Jang-Hyeon;Han, Won-Yong;Lee, Seung-U;Matsumoto, Toshio 71
MIRIS(Multipurpose InfraRed Imaging System)는 과학기술위성 3호의 주 탑재체이며 우주관측카메라, 지구관측카메라, 전장박스로 구성되어 있다. MIRIS 우주관측 카메라는 0.9-2.0${\mu}m$ 영역에서 3.67 deg.${\times}$ 3.67 deg. FOV로 우리 은하평면 survey 관측과 우주배경복사(CIB) 관측을 수행할 것이다. MIRIS는 2월 말에 비행모델 개발을 완료하였고, 향후 위성체와의 조립을 진행하고, 러시아 Dnepr 발사장으로 옮겨 2012년 하반기에 발사 예정이다. MIRIS 우주관측카메라에는 Teledyne PICNIC(256${\times}$ 256 pixel) array를 사용하였고, Dark current, Linearity, Read-out Noise, Gain, Flat 영상 측정 등의 calibration을 수행하였다. 본 발표에서는 Calibration 결과에 대해 논의 하고자 한다. -
Hinode/XRT has observed coronal mass ejections (CMEs) since it launched on Sep. 2006. Observing programs of Hinode/XRT, called 'CME watch', perform several binned observations to obtain large FOV observations with long exposure time that allows the detection of faint CME plasmas in high temperatures. Using those observations, we determine the upper limit to the mass of hot CME plasma using emission measure by assuming the observed plasma structure. In some events, an associated prominence eruption and CME plasma were observed in EUV observations as absorption or emission features. The absorption feature provides the lower limit to the cold mass while the emission feature provides the upper limit to the mass of observed CME plasma in X-ray and EUV passbands. In addition, some events were observed by coronagraph observations (SOHO/LASCO, STEREO/COR1) that allow the determination of total CME mass. However, some events were not observed by the coronagraphs possibly because of low density of the CME plasma. We present the mass constraints of CME plasma and associated prominence as determined by emission and absorption in EUV and X-ray passbands, then compare this mass to the total CME mass as derived from coronagraphs.
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타이탄의 근적외선 영역 스펙트럼에서 나타나는 특유의 넓은 흡수밴드를 고체 탄화수소화합물과 질소화합물의 조합으로 설명하고자 한다. 이 흡수 밴드는 대기권의 하층부에 존재하는 연무(haze)에 의한 것으로, 3.3 - 3.4 micron 부근과 2.30 - 2.35 micron 부근에서 유사한 형태가 발견됐다. 두 파장대 모두 C-H 스트레칭 모드가 존재하는 영역이라는 공통점이 있으며, 그 형태가 넓은 흡수밴드로 나타나므로 대기 중에 고체상태의 탄화수소화합물이 존재하는 것으로 유추할 수 있으며, 관련 분자들의 실험값과 복사전달모델을 이용하여 이를 설명하고자 한다. 또한, 이 흡수밴드는 고도에 따라 그 형태와 세기가 달라지므로, 연무 입자들의 고도에 따른 수직분포 및 크기 등을 파악할 수 있다. 이 연구에서는 기존에 타이탄에서 발견된
$CH_4$ ,$C_2H_6$ ,$CH_3CN$ 의 고체 분광선과, 해당 영역에서 흡수선을 보이는$C_5H_{12}$ ,$C_6H_{12}$ ,$C_6H_{14}$ 등의 고체 분광선을 이용한 모델을 Cassini 탐사선의 VIMS 관측자료로부터 유도한 파장 및 고도에 따른 광학적 깊이 변화량과 비교하여 보여주고자 한다. -
I will report recent progress in understanding properties of stellar and interstellar components of the Milky Way Galaxy on the two extremes - ongoing star formation activities in the Galactic center and stellar relics in the halo. Properties of the interstellar medium in the Galactic center and their relationship with star formation activities will be discussed based on by far the largest mid-IR spectroscopic data set in this region. Correlations between stellar kinematics and metallicities in the halo will be presented, along with a discussion on the estimation of fundamental stellar parameters from a set of empirically calibrated isochrones.
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We present the Yonsei Evolutionary Population Synthesis (YEPS) models for spectroscopic and photometric evolutions of simple and composite stellar populations. The models are based on the most up-to-date Yonsei-Yale stellar evolutionary tracks and BaSel 3.1 flux libraries, and provide integrated spectroscopic quantities of Lick/IDS system including high-order Balmer absorption-lines. Special care has been taken to incorporate the systematic variation of horizontal branch (HB) morphology as functions of metallicity, age, alpha-element mixture, and helium abundance of simple stellar populations. Our models for normal-helium stellar populations indicate that the realistic modeling of HB and alpha-element brings about 5 Gyr and 0.1 dex differences in age and metallicity estimations, respectively, compared to those without these effects. The HB effect does not depend on the specific choice of stellar libraries and alpha-element enhancements, and this effect is non-negligible even in the metal sensitive absorption indices, such as Mg2 and Mg b. Comparison of the models to observations reveals that the HB and alpha-element effects are critical in understanding otherwise inexplicable phenomena found in globular cluster systems in the Milky Way and nearby galaxies, including the observed bimodality of the line strengths of globular clusters in massive galaxies. In addition, we found that helium-enhanced stellar populations, which are the major sources of extreme HB stars, bring about increased FUV, NUV fluxes, and thus the model colors of those filters become extremely blue. Age dating based on the YEPS model with normal-helium stellar populations reveals that the evidence for 'downsizing' of elliptical galaxies is found not only in the local field but also in Coma cluster, and that the mean age of elliptical galaxies in Coma cluster is about 1.4 Gyr younger than the mean age of those in the local field. We also find that our models with helium-enhanced subpopulations can naturally reproduce the strong UV-upturns observed in giant elliptical galaxies assuming an age similar to that of old GCs in the Milky Way.
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Radial color gradient of disk galaxies has been a key tool for diagnosing the ages and metallicities of the stars and gas of these galaxies, and thus, the formation process of these disks. In many cases, observational data support the 'inside-out' picture of disk galaxy formation proposed by Larson (1976). In this scenario, gas within dark matter halos cools and accretes on to the outer disk while enhancing star formation in the disk. Recent discoveries of "extended ultra-viloet" (XUV) disks also show that majority of disk galaxy experience active star formation within out disks where gas surface density is quite low (Thilker et al. 2007; Gil de Paz et al. 2007). However, neither gas, nor stars stay put within galaxies. They rather migrate into bulges, disperse throughout galaxies, or flow into and out of galaxies via various mechanisms. There have been a few notable studies to investigate how radial star formation and metal abundance gradients vary across populations of disk galaxies systematically. However, the mechanisms driving gas transport are still poorly understood. Cross-matching various galaxy catalogs including KVAGC and UKIDSS, we are investigating if color gradients of late-type galaxies depend on their physical properties, especially on environmental properties. We will present the result from the pilot study on Karachentsev isolated galaxy catalog.
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Im, Myung-Shin;Jeon, Yi-Seul;Jang, Min-Sung;Choi, Chang-Su;Kang, Eu-Gene;Jun, Hyun-Sung;Urata, Yuji;Huang, Kui-Yun;Kruehler, Thomas;Sakamoto, Taka;Gehrels, Neil;Choi, Philip I.;Larger Collaboration, Larger Collaboration 32.2
Gamma Ray Bursts (GRBs) are the most energetic events in the universe, and are known to arise from the death of massive stars in many cases. Their extreme brightness makes it possible to detect them at very high redshift (z > 6.5), well into the epoch of re-ionization, providing us with an opportunity to investigate the deaths of the first stars when the universe was much younger than 1 Gyr. Here, we report the discovery of GRB 100905A, a GRB at$z$ - 7.5 (age of the universe at 700 Myr). Our observation revealed a strong spectral break between z and J band, allowing us to estimate its photometric redshift. Its gamma-ray light curve shows a very short duration of about 0.7 sec, the shortest duration event at z > 5. Investigation of this and three other known GRBs at z > 6.5 reveals that they are all short duration bursts. This is puzzling, considering that GRBs from death of massive stars do not show short duration. We suggest two possible explanations for this: (i) the BAT light curves of the high redshift GRBs suffered from observational selection effect where we are only observing the very tip of the light curve; (ii) the stars in the early universe had a peculiar nature that are different from ordinary stars at lower redshifts. -
We investigate the disk-jet connection of Young Radio Galaxies (YRGs) by comparing emission-line properties with radio luminosity and jet size. By combining new optical spectra for 21 objects with SDSS archival data for 15 objects, we selected a sample of 36 low-redshift YRGs at z < 0.4. We find that YRGs are classified in high- and low-excitation galaxies based on the relative strength of high-to-low excitation line strengths, suggesting that there are two populations in YRGs as similarly found in large radio galaxies, i.e., FRIs and FRIIs. High-excitation galaxies (HEGs) have higher emission line luminosities than low-excitation galaxies (LEGs) at fixed black hole mass and radio luminosity, suggesting that the Eddington ratio is higher in HEGs than in LEGs and that for given radio activity HEGs have higher accretion activity than LEGs. The difference between HEGs and LEGs is probably due to either mass accretion rate or radiative efficiency.
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Low-ionization nuclear emission-line region (LINER) galaxies constitute a major fraction of low-luminosity AGN population in the local Universe. In contrast to Seyfert galaxies, it is theoretically expected that LINERs would not have an outflow due to their low Eddington ratio. Using Keck/LRIS spectroscopy on a nearby LINER galaxy SDSS J091628.05+420818.7, we find a significant radial velocity offset for [OIII]
${\lambda}$ 5007 emission line as - 50 km$s^{-1}$ blueshifted compared to systemic velocity of the galaxy, while other emission lines exhibit no or little offset. The observed [OIII] velocity offset possibly indicates an outflow of gas in the LINER galaxy, and it is probable that we only detected the [OIII] velocity offset because [OIII] ionization region is closer to the accretion disk, hence, more affected by an outflow. We further investigate the [OIII] velocity offset of -4000 SDSS AGN-host galaxies to compare the strength of AGN outflow. We find that a number of both LINER and Seyfert galaxies show [OIII] velocity offset, but the fraction of LINER galaxies with velocity offset is smaller than that of Seyfert galaxies. The preliminary results imply the presence of gas outflow in LINER galaxies, although outflow strength is probably weaker compared to Seyfert galaxies. -
I present an analysis of the linear polarization of six active galactic nuclei (AGN). We monitored our targets from 2007 to 2011 in the observatory-frame frequency range 80-253 GHz with the Plateau de Bure Interferometer (PdBI). We find average degrees of polarization in the range 2-7%; this indicates that the polarization signals are effectively averaged out by the emitter geometries. We see indication for the presence of strong shocks and/or variability of the emitter geometries. We attempt to derive rotation measures for all sources, leading to actual measurements for two targets which find the highest rotation measures reported to date for AGN.
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In the context of structure formation in a hierarchical Universe, the relevance of mergers to radio-loud active galaxies is still under debate. I employ two different observational approaches to investigate the merger history of active galaxies, using several different samples of radio-loud AGN. I will first show results from the investigation of a complete sample of flat-spectrum radio-AGN and their role in a merger-driven evolution of galaxies. In the second part of my talk I will focus on the investigation of the close environment of radio-loud active galaxies, using data from the new VISTA-VIDEO near-infrared survey. Strong evidence is found supporting a close connection between merger events and radio-loud AGN.
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Determining the virial factor of the broad-line region (BLR) gas is crucial in calibrating AGN black hole mass estimators, since the measured line-of-sight velocity needs to be converted into the representative velocity of the BLR gas. The unknown virial factor has been empirically calibrated based on the
$M_{BH}-{\sigma}_*$ relation of non-AGN galaxies, but the claimed values are different by a factor of 2 in recent studies. We investigate the origin of the difference by measuring the$M_{BH}-{\sigma}_*$ relation using the most updated nearby galaxy sample, and explore the dependence of the virial factor on the various fitting methods. We find that the discrepancy is mostly caused by the sample bias while the difference stemming from various regression methods is marginal. Based on the best-determined virial factor, we present the updated$M_{BH}-{\sigma}_*$ relation of local active galaxies. -
According to the correlations between galaxy and black hole mass, the most massive galaxies harbor the most massive black holes, with a current mass limit of.
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Recent wide and deep surveys allow us to investigate the large scale structure of the Universe at high redshift. We present studies of the clustering of high redshift galaxies, using reprocessed UKIDSS DXS catalogue. We measure the angular correlation function of high redshift galaxies which is Extremely Red Objects (EROs). Firstly we found that their angular correlation functions can be described by a broken power-law. We also found that red or bright samples are more strongly clustered than those having the opposite characteristics, and that old, passive EROs are found to be more clustered than dustry, star-forming EROs. Additionally the average halo mass and other properties were estimated using the halo model. Finally the observed clustering of EROs was compared with predictions from the cosmological simulation.
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The aim of this study was to explore the role of galaxy mergers on the formation and evolution of galaxies in galaxy clusters. For this purpose, u', g', r' deep optical imaging and multi-object spectroscopic observation were done for four rich Abell clusters at z
${\lesssim}$ 0.1 (A119, A2670, A3330, and A389) with a MOSAIC 2 CCD and Hydra spectrograph mounted on a Blanco 4-m telescope at CTIO. With the deep images, we found that about 25% of the bright red-sequence galaxies exhibited post-merger signatures in a cluster environment. This fraction was much higher than what was expected from the results of the field environment (-35%, van Dokkum 2005) and significantly low on-going merger fractions (about one-fifth of the field) appeared in the clusters currently. Taking advantage of the most up-to-date semi-analytic model, the results indicate that most of the post-merger galaxies may have carried over their merger features from their previous halo environment. All the brightest cluster galaxies in our cluster samples revealed faint structures in their halos as well as multiple nuclei in their centers seen in the deep optical images. We suggest that the mass of the BCGs increased mainly though major mergers at recent epochs based on their post-merger signatures and the large gaps in the total magnitudes between the BCGs and the second-rank BCGs. A UV bright tidal tail and tidal dwarf galaxy (TDG) candidates around the post-merger galaxy, NGC 4922, were discovered in the outskirts of the Coma cluster using the GALEX UV data. We did two-component stellar population modeling for the TDG candidates and the results indicate that they are an early form of dwarf galaxies frequently found around massive early-type galaxies in clusters. In conclusion, we suggest that the mergers of galaxies are an important driving force behind galaxy formation and evolution in cluster environments even until recent epochs. -
We present mid-IR (MIR) and near-UV (NUV) properties of red sequence galaxies defined by optical color-magnitude relation. We use the Wide-field Infrared Survey Explorer (WISE) preliminary released data matched with the SDSS DR7/GALEX GR6. The red sequence galaxies with little emission lines show a wide spread of MIR (3.4um-12um) colors, implying a variety of MIR excess emission. We focus on the properties of the red sequence galaxies with MIR excess, comparing the properties of post-starburst galaxies to trace how galaxies migrate to the red sequence.
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The A2199 supercluster at z=0.03 is one of the most massive system in nearby universe. In this supercluster, A2199 is kinematically connected to A2197 and several infalling galaxy groups. Thanks to a high-density environment and complex structures around A2199, this supercluster is an excellent laboratory for studying galaxy evolution. We determine the membership of galaxies in the supercluster using radial velocities of galaxies drawn from the SDSS spectroscopic DR7 data. We present an infrared view of this supercluster using AKARI and WISE data. We compare spatial distributions between early- and late-type galaxies, and also AGNs and star-forming galaxies. We also investigate how local and cluster-scale environments affect galaxy properties, such as IR-properties, star formation rates, and morphology transformations.
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우주의 초기조건, 현재 그리고 미래를 정밀하게 예측하기 위한 관측 프로젝트들이 하나 둘씩 현실화 되어 가고 있다. 이러한 프로젝트 중의 하나인 분광 광시야 관측을 이용하여 우주론적인 질문에 대한 해답을 얻는 방법을 논의한다. 분광 광시야 관측에는 밀도 섭동과 고유 속도에 관련된 정보가 모두 포함되어 있는데, 아직 고유속도에 대한 정보를 어떻게 얻을 수 있는지에 대한 방법론을 확정하지 못하고 있다. 우리는 지난 이 삼 년 간의 연작형식의 논문을 통하여 새로운 방법을 개척했고, 그 방법을 미래의 정밀한 관측에도 적용하기 위해서 노력하고 있다. 이러한 노력은 우주가속팽창의 원인규명에 큰 공헌을 할 것이고, 우주가 팽창한 역사를 이론적인 모델에 독립적으로 관측할 수 있는 가능성을 열 것이다. 이 발표를 통하여, 분광 광시야 관측의 우주론적인 의미, 관측된 자료를 분석할 수 있는 새로운 방법, 그리고 미래에 예정된 정밀한 관측 프로젝트들에 대해서 논의한다.
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We use two-dimensional high-resolution MHD simulations to investigate the effects of magnetic fields on the formation and evolution of such substructures as well as on the mass inflow rates to the galaxy center. We find that there exists an outermost x1-orbit relative to which gaseous responses to an imposed stellar bar potential are completely different between inside and outside. Inside this orbit, gas is shocked into dust lanes and infalls to form a nuclear ring. Magnetic fields are compressed in dust lanes, reducing their peak density. Magnetic stress removes further angular momentum of the gas at the shocks and leads to a smaller and more centrally distributed ring, resulting in the mass inflow rates larger, by more than two orders of magnitude, than in the unmagnetized counterparts. Outside the outermost x1-orbit, on the other hand, an MHD dynamo operates near the corotation and bar-end regions, efficiently amplifying magnetic fields. The amplified fields shape into trailing magnetic arms with strong fields and low density. The base of the magnetic arms have a thin layer in which magnetic fields with opposite polarity reconnect via a tearing-mode instability. This produces numerous magnetic islands with large density which propagate along the arms to turn the outer disk into a highly chaotic state.
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Nuclear rings in barred galaxies are sites of active star formation (SF). We investigate SF and its feedback effects occurring in barred galaxies, for the first time, using high-resolution grid-based hydrodynamic simulations. The gaseous medium is assumed to be infinitesimally thin, isothermal, and unmagnetized. The SF recipes include a density threshold corresponding to the Jeans condition, a SF efficiency of 1%, and momentum feedback via Type II supernova events together with stellar-wind mass loss. To investigate various environments, we vary the gas sound speed as well as the efficiency of momentum injection in the in-plane direction. We find that when the sound speed is small, the surface density of a ring becomes largely independent of the azimuthal angle, resulting in star-forming regions distributed over the whole length of the ring. When the sound speed is large, on the other hand, the ring achieves the largest density at the contact points between the dust lanes and the ring where SF occurs preferentially, leading to a clear age gradient of star clusters in the azimuthal direction. Since rings shrink with time, a radial age gradient of star clusters naturally develop regardless of sound speed, consistent with observations. SF persists over 200 Myr, with an average rate of
${\sim}1.3M_{\odot}/yr$ similar to observed values. Rings gradually become hostile to SF as they lose gas into stars and turbulent motions dominate. -
We present our study on a comparison of dark matter halo merger history from the runs using different numerical simulation codes. To analyze the uncertainty caused by the use of different N-body calculation methods, we compare the results from two cosmological hydrodynamic simulation codes GADGET-2 and RAMSES, which use a TreePM algorithm and the Adaptive Mesh Refinement(AMR) technique respectively. We perform cosmological dark matter-only simulations with the same parameter set and initial condition for both. The dark matter halo mass functions from two simulation runs correspond well with each other, except for lower mass haloes. The discrepancy on the low-mass haloes in turn causes a notable difference in halo merger rate, especially for the case of extremely minor merger. The result from GADGET-2 predicts that most haloes undergo more number of mergers with small haloes than that from RAMSES, independent of halo mass and environment. However, in the context of the study on galaxy evolution, such extreme minor mergers generally do not have strong effects on galaxy properties such as morphology or star formation history. Hence, we suggest that this uncertainty could be quantitatively negligible, and the results from two simulations are reliable even with only minor difference in merger history.
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In the hierarchical universe, galaxy merger is predicted to be frequent, and thus it is an important element for understanding galaxy evolution. In particular, star formation is greatly enhanced during the merger. The aim of this study is to understand the position and rate change of star formation caused by equal-mass edge-on mergers. We use the GADGET2- N-body/SPH code, and fully consider gas cooling, star formation, and supernova feedback. We show the star formation rate (SFR), and the magnitude and color evolution of the merger remnants for 18 different configurations varying orbit elements and inclinations of host galaxies against orbit planes. Then we construct the mock images of the remnants and investigate on how equal-mass galaxy merger affects the SFR and color/magnitude evolution while considering dust reddening. We conclude that over 90% mass of SF in equal-mass merger is in the central region. SF in tidal feature involves a small fraction of new stars and thus is difficult to detect unless deep imaging is performed. Around 55
${\pm}$ 5 percent of gas turns into stars until the final coalescence which typically corresponds to 0.8, 1.2, and 2.5 Gyr for direct, parabolic, and elliptical orbit, respectively. This result is roughly consistent with Cox et al. 2000. We plan to implement this result into semi-analytic model of galaxy formation. Caveats and future work on merging conditions are discussed. -
Early-type dwarf galaxies are the most numerous galaxies in dense environments, making them ideal probes of the mechanisms that govern galaxy formation and evolution. Despite the common picture of an early-type dwarf galaxy as a quiescent one with no star formation and little gas, recent systematic investigations of early-type dwarf galaxies in the cluster revealed an unexpected variety among these apparently simple objects. In this talk, I review intriguing complexity of early-type dwarf galaxies in the cluster. I will also briefly introduce a new catalog of galaxies in the Virgo cluster using SDSS data, extended Virgo Cluster Catalog (EVCC).
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Interactions between the galactic interstellar medium (ISM) and the intra cluster medium (ICM) are believed to be one of the main processes affecting galaxy evolution in cluster environments. The aim of our research is to study the molecular gas properties of a galaxy under the ICM pressure in the cluster environment. It has been well known that cluster galaxies are deficient in atomic hydrogen gas (HI gas) compared to their field counterparts and now there is much evidence that low density ISM is being removed by ram pressure due to ICM wind. Meanwhile, no significant molecular gas deficiency of the cluster galaxy population has been found yet they show overall lower star formation rate than galaxies in the field, and it is still puzzling how the star formation could decrease without stripping of dense molecular gas. To address this issue, we probe the detailed molecular gas properties of NGC 4402, located near the cluster center, as part of a study of four spiral galaxies in the Virgo Cluster. NGC 4402 is well known undergoing ram pressure stripping with a truncated HI disk(
$D_{HI}/D_{opt}$ - 0.75 and only 36% of HI gas compare to field galaxies of a similar size) and a disturbed gas morphology. Comparing the high resolution 12CO and 13CO data of NGC 4402 from the Sub Millimeter Array (SMA) with existing other wavelength data, we probe the spatial distribution and a physical condition of molecular gas under strong ICM pressure. We discuss the star formation activity might have been altered and hence how the global color of NGC4402 would change in the future. -
It has been suggested that merging plays an important role in the formation and the evolution of early-type galaxies (ETGs). Optical-NIR color gradients of ETGs in high density environments are found to be less steep than those of ETGs in low density environments, hinting frequent merger activities in ETGs in high density environments. In order to examine if the flat color gradients are the result of dry mergers, we studied the relations between merging features, luminosities, environments and color gradients of 196 low redshift ETGs selected from Sloan Digital Sky Survey (SDSS) Stripe82. Near Infrared (NIR) images are taken from UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Color (r-K) gradients of ETGs with tidal features are a little flatter than relaxed ETGs, but not significant. We found that massive (> 10^11.3 solar masses) ETGs have -40% less scattered color gradients than less massive ETGs. The less scattered color gradients of massive ETGs could be evidence of dry merger processes in the evolution of massive ETGs. We found no relation between color gradients of ETGs and their environments.
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We have performed our first cosmological hydrodynamic simulation using the recently developed SPH+GOPTM code that includes radiative cooling/heating, star formation, and supernova feedback. Here we present preliminary results from the simulation
$3.4{\times}10^4M_{\odot}$ , thus sub-galactic structures, such as satellite galaxies and globular clusters around a host galaxy, can be resolved with more than hundred particles. We follow formation and evolution of the sub-galactic structures in view of their star formation history, merging/accretion rate, and origins. -
We examine the distribution and properties of shock waves within a couple of Mpc from cluster center with single-level grid simulations using up to 20483 grid zones. The effects of cooling/heating and feedbacks from galaxies are also incorporated. There are two different populations of shocks, merger shocks and accretion shocks. We discuss the manifestation of shocks through radio relics.
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Clusters of galaxies are the largest virialized structures in the universe, which serve as laboratories for the study of astrophysical processes on very large scales. Observations and theoretical arguments suggest that intracluster media is turbulent. The media are very hot and dynamic, highly rarefied, and probably magnetized at some level. The physics involved is complex and high-resolution simulations help us understand the physics and consequent phenomena. We are engaged in a simulation study designed to understand in this context how subsonic turbulence with very weak initial magnetic fields develops and evolves with imposed forcing. We find that the resulting turbulence is sensitive to the nature of forcing as well as the dissipation properties of the media.
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Cosmological shock waves result from supersonic flow motions induced by hierarchical clustering during the large-scale structure formation in the Universe. Suprathermal particles are known to be produced via plasma interactions at collisionless shocks in tenuous plasmas and they can be further accelerated to become cosmic rays (CRs) via diffusive shock acceleration (DSA). The presence of CR electrons has been inferred from observations of diffuse radio halos and relics in some merging galaxy clusters. We have calculated the emissions from CR electrons accelerated at weak planar shocks, using time-dependent DSA simulations that include energy losses via synchrotron emission and Inverse Compton scattering. The simulated nonthermal emission are used to model the synchrotron emission from several observed radio relics.
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은하의 형태학적 진화 양상을 분석하기 위해 허블 울트라 딥 필드 (Hubble Ultra Deep Field; HUDF)에 있는 밝은 은하를 조사하였다. Coe et al. (2006)의 HUDF 카탈로그에 포함된 적색편이, 적경, 적위, 밝기 등급, 픽셀 면적 값을 사용하여 HUDF은하의 B필터 영상에서 밝은 순서로 1000개의 천체를 선택하고 이로부터 939개의 은하의 육안 분류를 수행하였다. Elmegreen et al. (2005)의 분류 방법에 기초하여 타원 은하, 렌즈 은하, 나선 은하, 올챙이 은하(Tadpole), 이중 은하(Double), 사슬 은하(Chain), 덩어리 은하(Clump cluster)와 그 외의 불규칙 은하로 분류하였다. 이렇게 분류된 은하의 분류형과 은하의 적색이동 사이의 관계를 분석하여 HUDF 은하의 적색편이에 따른 형태학적 진화 양상을 찾아낼 수 있었다. 올챙이 은하, 이중 은하, 사슬형 은하, 덩어리 은하 등 병합 단계에 있는 것으로 추정되는 은하들은 적색편이가 작을수록 그 수가 대체로 감소하는 경향을 보이는 반면, 나선은하들은 적색편이가 작을수록 그 수가 증가하는 경향을 보였다. 또한, 적색편이와 은하 크기 사이의 관계를 보았을 때 낮은 적색 편이에서 나타나는 상대적으로 큰 은하들이 대부분 나선 은하였으며 이러한 결과는 은하 생성의 Bottom-Up 가설로 설명이 가능하다. 이와 함께 은하 형태의 정량적 분석을 위해 각 은하의 CAS와 함께 M20, Gini Coefficient(G)를 구하여 이들과 육안 분류와의 관계를 분석하여, CASGM20, 으로부터 은하의 분류 형을 찾는 방법을 모색하였다.
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We present preliminary report for spectral features of SN2011fe(type Ia) in M101 which was detected since late August of 2011.High-resolution spectra were obtained with BOES at the 1.8m telescope in BOAO.A number of Ca II, SiII, SII, OI, MgII, and FeII components are detected at different epochs and evolved.
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A unique ensemble of datasets is available for the AKARI North Ecliptic Pole (NEP) field, having being observed virtually across the whole electromagnetic spectrum. We have undertaken a study of radio sources in the NEP field and in particular radio-loud AGN. We present preliminary results concerning the identification of these radio-loud AGN using a host of different selection criteria. We aim to study the host galaxies of these systems within the current framework of galaxy evolution and the role that AGN play in it.
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The black hole mass-stellar velocity dispersion (
$M_{BH}-{\sigma}_*$ ) relation observed in the present-day universe has motivated numerous studies on the black hole-galaxy co-evolution. It is crucial to define the$M_{BH}-{\sigma}_*$ local active galaxies since cosmic evolution of the correlations is calibrated based on the local relation. However, stellar velocity dispersion is difficult to measure in active galaxies due to much higher AGN continuum than stellar pseudo-continuum, resulting in a small sample with reliable velocity dispersion measurements for studying the AGN$M_{BH}-{\sigma}_*$ relation. To increase the sample size and improve the measurements, we obtained high S/N near-IR spectra for 3 local AGNs, i.e., NGC 3227, Akn 120, 3C 390.3, for which reverberation black hole masses are measured, using the TripleSpec at the Palomar 5-m Telescope. By investigating aperture effect and correcting for rotation component, we determine the luminosity-weighted${\sigma}_*$ , based on the spatially resolved kinematics and compare them with optical measurements from literature. Combining our new measurements with literature data, we present an improved$M_{BH}-{\sigma}_*$ relation for the enlarged sample of reverberation-mapped AGNs. -
Given high accretion rates close to the Eddington limit, narrow-line Seyfert 1 galaxies (NLS1) are arguably the most important AGN subclass in investigating the origin of the black hole mass-galaxy stellar velocity dispersion (
$M_{BH}-{\sigma}$ ) relation. Currently, it is highly debated whether NLS1s are offset from the local$M_{BH}-{\sigma}$ relation. The controversy mainly comes from the fact that the [OIII] line width has been used as a proxy for stellar velocity dispersion due to the difficulty of measuring stellar velocity dispersion in NLS1s. Using the SDSS spectra of a sample of 105 NLS1, we performed multi-component fitting analysis to separate stellar absorption lines from strong AGN [FeII] complex in order to directly measure stellar velocity dispersion. We will present the result of decomposition analysis and discuss whether NLS1s follow the same$M_{BH}-{\sigma}$ relation based on the direct measurements of stellar velocity dispersion. -
Using deep images taken at Maidanak 1.5m telescope, at McDonald 2.1m telescope and Canada-France-Hawaii Telescope, Dupont 2.5m telescope we investigated the fraction of merging galaxies in hosts of 39 AGN which are brighter than M = -22 mag and nearer than z = 0.3. We found that 16 to 17 of 39 AGN host galaxies show the evidence of mergers like tidal tail, shell via careful visual inspection. We also studied with the merging fraction of a control sample, SDSS Stripe82 early type galaxies of which surface brightness limit and bulge magnitude are similar to that of the AGN sample. We found that merging fraction of the AGN sample is higher than that of early type galaxy samples in the whole range of bulge magnitude. This result implies that AGN activity may be correlated with merging. We also investigated the detailed morphology of merging feature. At least - 1/4 of control samples classified as a tidal and tidal+dust are shell structures. On the other hand only one (5.9%) of AGN sample classified as merger shows shell structures, and almost all merging AGNs show tidal tail features. From point of view that tidal tail may be at the early stage of merging, and shell may be at the late stage of mergers, this result suggests that AGN might be evolved into early-type galaxies after merging.
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Lee, Chang-Hui;Jeong, Hyeon-Jin;O, Gyu-Seok;Jeong, Cheol;Lee, Jun-Hyeop;Kim, Sang-Cheol;Gyeong, Jae-Man 48.1
We present the ultraviolet (UV) color-color relation of early-type galaxies (ETGs) in the nearby universe (0.05 < z < 0.12) to investigate the properties of hot stellar populations responsible for the UV excess (UVX). The initial sample of ETGs is selected by the spectroscopic redshift and the morphology parameter from the SDSS DR 7, and then cross-matched with the GALEX far-UV (FUV) and near-UV (NUV) GR6 data. The cross-matched ETG sample is further classified by their emission line characteristics in the optical spectra into quiescent, star-forming, and active galactic nucleus categories. Contaminations from early-type spiral galaxies, mergers, and morphologically disturbed galaxies are removed by visual inspection. By drawing the FUV-NUV (as a measure of UV spectral shape) versus FUV-r (as a measure of UVX strength) diagram for the final sample of -3700 quiescent ETGs, we find that the "old and dead" ETGs consist of a well-defined sequence in UV colors, the "UV red sequence," so that the stronger UVX galaxies should have a harder UV spectral shape systematically. However, the observed UV spectral slope is too steep to be reproduced by the canonical stellar population models in which the UV flux is mainly controlled by age or metallicity parameters. Moreover, 2 mag of color spreads both in FUV-NUV and FUV-r appear to be ubiquitous among any subsets in distance or luminosity. This implies that the UVX in ETGs could be driven by yet another parameter which might be even more influential than age or metallicity. -
We present preliminary results of a statistical study on the nuclear activity of compact group galaxies. What triggers Active Galactic Nuclei (AGN) is still a puzzling problem. One of the suggested AGN triggering mechanisms is galaxy-galaxy interaction. Many simulations have shown that gas can be supplied to the center of galaxies during galaxy encounters. In this regard, compact groups of galaxies are an ideal laboratory for studying the connection between galaxy interaction and nuclear activity because of their high densities and low velocity dispersions. We study the environmental dependence of the activity in galactic nuclei using 59 compact groups in the SDSS DR6. Using the emission line data, we classify galaxies in the compact groups. We find that 19% of the compact group galaxies are pure star-forming nuclei, 10% as transition objects, and only 7% of the galaxies in compact groups show the nuclear activity. The AGN fraction of compact group is higher than galaxy clusters, but lower than field environment. Implications of this result will be discussed.
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Recently it is found that the globular clusters are not only bound in their host galaxies, but also are wandering between galaxies in Virgo and Coma clusters. The cluster-wide distribution of these intracluster globular clusters (IGCs) suggests that IGCs are an important probe to understand hierarchical structure formation. We present a survey of IGCs in Virgo cluster using HST archive images for four HST/ACS fields located from about 9 arcmin to 40 acrmin from the cluster center. We find ten new IGCs and confirm four previously known IGCs. The number density of IGCs decreases as the distance from the cluster center increases. We derive integrated photometry of IGCs. We also obtain photometry of resolved stars in the outer region of each cluster. These IGCs are fainter than
$M_V{\approx}-9.5$ and mostly blue in (V-I) color. showing that they are mostly metal poor. The locations of red giant branch stars of IGCs in color-magnitude diagrams also show that they are meal-poor. We discuss the implications of these results. -
We present an investigation of X-ray hot gas halo in 12 isolated early-type galaxies from cross-matched sample of XMM-Newton and SDSS DR 7(0.025 < z < 0.08588 and Mr <-19.5). Isolated galaxies that the separation between galaxy and the closest neighbor is farther than its virial radius are not affected by environments, and their X-ray hot gas halo can be studied without contribution of intragalactic medium in all circumstances. We find that isolated galaxies in low density have correlation of
$L_X-L_R$ and those in high density have no trend. This suggests that internal process is much effective in low density and environmental effects play important role of this relationship in high density. We also find the galaxies affected by environments in the large scale structure. In this paper, we report preliminary results for the study. -
As a tracer of star formation history, metallicity provides crucial information for understanding galaxy evolution. In the case AGN, gas metallicity is often derived from the flux ratio of UV emission lines, i.e., NV1240 and CIV1549. To investigate the dependence of metallicity on AGN luminosity, black hole mass, and accretion rate, we measure NV1240 and CIV1549 line fluxes and derive gas metallicity of a sample of 73 local Seyfert 1 galaxies and QSOs, using archival UV spectra obtained with the HST and IUE. In this work, we will present the metallicity of local AGN and its relation with AGN properties.
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We present the results of near infrared (2.5-5 micron) spectroscopy of nearby luminous infrared galaxies (LIRGs) using AKARI. The LIRG catalog is constructed from the cross-correlation between the Infrared Astronomical Satellite and the Sloan Digital Sky Survey data, and optically non-Seyfert type LIRGs are selected for main targets. We search for optically elusive active galactic nuclei (AGNs), based on the strengths of 3.3 micron polycyclic aromatic hydrocarbon emission and dust absorption features at 3-4 micron. We investigate the hidden AGN fraction as a function of the infrared luminosity and correlation between optical and near infrared star formation indicators.
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We observed low-z quasar PG1426+015 (z=0.086), using the near-IR high resolution echelle spectrometer, IRCS, at the SUBARU 8.2 m telescope. Using an Adoptive Optics system, the full width at half maximum of the point spread function was about 0.3 arcsec, which can effectively separate the quasar spectra from the host galaxy spectra. We also maximize the total exposure time up to several hours per target, and develop data reduction methods to increase the signal-to-noise ratios. This poster presents the data reduction processes and sample spectra from the quasar and its host galaxy. These spectral lines will be used to study the physical mechanism of quasars, and the velocity dispersions of the stars in the bugle of the host galaxy.
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Red Active Galactic Nuclei (AGNs) are suspected to intermediate stage between ULIRG and AGN phase. As well as, red AGNs are suspected to have more than 50% of whole AGN population. For understanding the characteristics of red AGN, Black Hole (BH) mass is a key property and can not be estimated by existed method such as reverberation mapping and single epoch method using 5100A continuum and Balmer lines. Thus we still don't know their characteristics and properties in clearly. To estimate properties of red AGNs without the effect of dust extinction, we obtained Near InfraRed (NIR) spectra of 31 reverberation mapped AGNs and 49 Palomar-Green(PG) Quasi-Stellar Objects (QSOs) by using the infrared camera (IRC) of AKARI space telescope with unique wavelength range 2.5-5.0
${\mu}m$ . Upon this spectra, we measured the FWHM and luminosity of Brackett${\alpha}$ and${\beta}$ lines for deriving new BH mass estimators of AGNs. -
It is often said that there is little geometrical mind in Korean history. However, a method to project the surface of a sphere onto 2-dimensional plain was applied to the representative Korean star chart or Cheonsang Yeolcha Bunyajido (天象列次分野之圖). The method, called the equi-distant polar projection, was explained in detail in ancient Chinese history book of the Tang dynasty, which was originated from older history. Another method of the Mercator projection was introduced by the famous engineer Su Song (蘇頌) of the Song dynasty. The description has quite geometrical thoughts, especially the concept of infinity or convergence appears, However, this type of sky projection method was not widely used in east Asia. When the European Jesuits came to China to evangelize the Chinese people, they found that the Chinese people paid much attention to advanced European astronomical knowledge. Thus, they introduced the European astronomical knowledges into China, and the star chart was one of them. The projection method of the new charts were quite different from the Chinese tradition. When the Koreans brought those new star chart from China, they must have known the geometrical description of the method. The method was described in detail in a volume of Chongzhen Lishi (崇禎曆書) or Xiyang Xinfa Lishu (西洋新法曆書). The explanation consists of three part. One is the quantitative way; another is a geometrical way using axiomatic systems; and the other is the practical method to draw star chart with the geometical projection. However, when we see the Honcheon Jeondo (渾天全圖) that is thought to be duplicated by Kim Jeongho (金正浩), the new geometrical method was not so widely known to the Koreans. I will discuss the reason why the geometrical minds have not been widely adopted in the Korean civilization.
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1438년 장영실은 경복궁 흠경각(欽敬閣) 내부에 자동물시계인 옥루(玉漏)를 제작하였다. 흠경각루(欽敬閣漏)는 수격식(水激式, 물의 흐름을 이용하여 수차를 운행하는 동력방식)으로 운영되는 것으로 중국의 수운의상대(水運儀象臺, 1092년경 제작)의 수격방식과 유사하다. 하지만 동력 방식을 제외한 내부 구조에 대한 것은 흠경각루의 외형모습인 가산 형태, 시보인형의 구성과 배치, 작동구조 등에 의해 결정된다. 장영실은 흠경각루의 내부 기어장치의 구성과 연결 등에 대해서 새로운 제작기술을 사용하였다. 우리는 수격식 동력 방식에서 내부 공간에 따른 각각 운행 장치들의 구성과 동력전달체계에 대하여 분석하였다. 또한 수차가 일정한 회전력을 갖도록 제어하는 천형(天衡) 장치에 대하여 고찰하였다.
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현재 국내에는 약 40여 개의 종합(관측실과 투영관이 있는) 천문시설이 운영 중에 있으며 새로운 시설이 꾸준히 추가로 건설 되고 있다. 그리고 교육과학연구원, 도서관 등 많은 시설에서 천문시설을 갖추고 교육에 활용하고 있다. 그런데 대부분의 천문시설에서는 별자리 설명, 천체투영관에서의 영상물 상영, 그리고 천체망원경을 이용한 관측실습 등 한정된 소재와 일관된 형식의 천문교육 프로그램을 운영 하고 있다. 하지만 국립과천과학관에서 방학 중 천문학교실을 운영해본 결과 좀 더 깊이 있는 천문학 교육에 대한 수요가 상당히 많다는 사실을 확인할 수 있었다. 실제 과학교육 현장에서는 여러 분야의 다양한 교육프로그램들이 개발되어 운영되고 있으나 천문학을 주제로 한 교육은 찾아보기 어려운 상황이다. 천문학은 새로운 연구 결과가 가장 활발하게 발표되는 분야들 중 하나로, 일반인이나 언론에서도 상당히 많은 관심을 보여주고 있다. 외계행성 탐사, 초신성 관측, 우주 가속팽창과 같은 최신 천문학 분야의 다양한 주제들을 이용하여 교육프로그램을 개발하면 일반인들에게 천문학의 내용을 알리는데 좋은 기회가 될 수 있을 것이다. 국립과천과학관에서는 방학 프로그램에 이어 조금 더 심화된 교육프로그램을 기획하여 운영할 준비를 하고 있다. 현재 국립과천과학관에서 준비 중인 천문교육프로그램을 소개하고 여러 사람들의 의견을 들어보고자 한다.
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디지털 천체투영기의 보급은 천체투영관의 운영과 교육적 활용 방법에 변화를 가져왔다. 돔영상물 상영이 가능한 디지털 천체투영기를 도입한 천체투영관들의 교육적 활용을 높이기 위해서는 영상물을 활용한 교육 콘텐츠 개발이 선행되어야 하다. 이번 연구에서는 1)AMNH(American Museum of Natural History)에서 사용되고 있는 돔영상물의 교육자 매뉴얼들을 사례조사 하였고, 2)사례조사 결과와 2007 개정 과학과 교육과정을 고려하여 돔영상물 Planets(Astronef Production제작, 2010)의 교육자 매뉴얼을 개발 하였다. 개발된 Planets 교육자 매뉴얼의 활용은 개관 예정인 국립대구과학관과 국립광주과학관 천체투영관의 운영 활성화와 교육활동을 극대화 할 수 있을 것으로 기대된다. 또한 국내에서 수행중인 천문학 프로젝트(KVN, GMT, KMTNet, SKA 등)들의 교육자 매뉴얼 제작에 참고자료로 활용되길 기대한다.
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2010년과 2011년의 관측시즌에 총 23일의 BVR 측광 관측을 통하여 처음으로 얻은 2세트의 BVR 광도 곡선을 분석하였다. 새로운 두 세트의 BVR 광도곡선은 제1식과 제2식의 깊이가 거의 비슷하지만, 식바깥 부분에서 관측 시즌에 따라 서로 다른 모양의 잘 발달된 파형 모양을 보인다. 이는 BD And가 흑점이 활동이 매우 심한 짧은 주기의 RS CVn형 식쌍성임을 나타내는 것이다. 우리의 극심시각을 포함한 모든 극심시각을 분석하여 BD And의 공전주기가 규칙적으로 변하는 것을 발견하였다. 이 변화를 보이지 않는 제3천체에 의한 광시간 효과로 가정하여, 궤도이심율이 0.83이며, 9.15년의 주기를 가진 광시간 궤도를 결정하였다. Wilson-Devinney 쌍성 모형을 이용하여 흑점과 제3광도를 고려한 두 세트의 광도곡선 해를 산출하였고, BD And의 절대량을 구하였다. 식바깥의 파형 모양의 변화는 주성의 표면에 매우 큰 두 개의 흑점과 그 위치와 이동으로 잘 설명되며, 전체 광도의 약 15%에 해당되는 제3광도가 검출되었다. 주기연구에서 구한 제3천체의 궤도요소와 제3광도의 결합으로 제3천체의 질량과 궤도경사각을 유추하였다. BD And의 성분별의 평균 나이가 등연령 곡선으로부터 태양과 비슷한 4.6
${\times}$ 109년으로 산출되었다. BD And를 포함하여 현재까지 알려진 짧은 주기의 RS CVn형 쌍성들의 H-R도가 항성진화 경로와 함께 제시되며, 그 천체물리학적 의미를 살펴본다. -
Silicate-carbon stars are characterized by oxygen-rich (O-rich) dust features despite their carbon-rich (C-rich) photospheres. While the origin of silicate-carbon stars has been a mystery ever since their discovery, the most widely accepted hypothesis is that the silicate-carbon stars have a low-luminosity companion and the O-rich material is stored in a circumbinary disk or a circumstellar disk even after the primary star becomes a carbon star. In order to study the properties of circumstellar dust envelopes of silicate-carbon stars, we perform radiative transfer model calculations using RADMC-3D with an axi-symmetric dust density distribution (a disk) as well as a spherically symmetric dust distribution. For various dust envelope models with different shapes and chemistry, we calculate the model spectral energy distributions (SEDs) and compare the model results with the observed SEDs of selected 5 silicate-carbon stars. The Circumstellar disk models are fairly well fitted with the observational data of 5 silicate-carbon stars. We find some evidences that the circumbinary disk model could be a better explanation for the origin of silicate carbon stars than the simple detached silicate dust shell model of the transition phase of the stellar chemistry.
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구경 3.6m CFHT 관측으로 얻은 산개성단 NGC 1245와 NGC 2506의 측광결과를 이용하여 두 성단의 역학적 진화와 헤일로 구조를 연구하였다. 이를 위하여 우리는 별들의 색-등급 도상의 위치와 천구 상에서의 위치를 동시에 고려하여, 각 별들에 대한 측광학적 구성원 확률을 정의하는 방법을 개발하였다. 이 방법을 사용하여 얻어진 구성원 확률을 이용하여 성단의 반경에 따른 구성원 별들의 광도함수와 반경에 따른 별들의 유효개수밀도 분포를 구하였다. 이들로부터 우리는 두 성단에서 질량분리현상을 확인하였으며, 성단에서 증발한 별들에 의해 형성된 헤일로의 존재를 알 수 있었다. 또한, 각 성단들의 공간상에 투영된 유효개수밀도 분포를 분석하여, 두 성단 모두 형태가 찌그러져 있으며 그 방향은 은하면과 관련이 적음을 보였다. 본 발표에서는 새로 개발한 구성원 확률을 정의하는 방법 및 두 성단의 역학적 진화와 헤일로 구조에 대한 내용을 소개하고자 한다.
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We present a study of the asymptotic giant branch (AGB) contribution to the total Ks band luminosity of star clusters in the Large Magellanic Cloud (LMC) as a function of age. AGB stars, a representative intermediate-age population, are a strong source of NIR to MIR emission so that they are a critical component for understanding the near-to-mid infrared observation of galaxies. Current calibration of IR emission in evolutionary population synthesis (EPS) models for galaxies is mainly based on a small number of LMC star clusters. However, each LMC star cluster with intermediate age contains only a few AGB stars so that it suffers from a stochastic effect. Therefore a large number of them are needed for solid calibration of the EPS models. We study physical properties of a large number of LMC star clusters to estimate the Ks band luminosity fraction of AGB stars in star clusters as a function of age. We discuss the stochastic effect in calibrating models, and the importance of this calibration for studying the evolution of not only nearby galaxies but also of high-z galaxies.
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We present a spectroscopic study of the globular clusters (GCs) in the giant elliptical galaxy (gE) M86 in the Virgo galaxy cluster. Using the spectra obtained from the Multi-Object Spectroscopy (MOS) mode of Faint Object Camera and Spectrograph (FOCAS) on the Subaru Telescope, we measured the radial velocities of 25 GCs, the metallicities of 16 GCs, and the ages of 8 GCs in M86. The mean velocity and the vocity dispersion of the GCs are <
${\upsilon}_p$ > = -354${\pm}$ 80 km/s and${\sigma}_p$ = 292${\pm}$ 32km/s, respectively. The M86 GC system shows some rotation with a large uncertainty and the velocity dispersion of the blue GC system is 60 km/s larger than that of the red GC system. The mean metallicity and age of M86 GCs are <[Fe/H]> = -1.13${\pm}$ 0.47 and= 9.7 ${\pm}$ 4.0 Gyr, respectively. We found one GC younger than 5 Gyr. We discuss the spectroscopic results of the M86 GC system in comparison with the GC systems in other gEs. -
We present a survey for finding hidden star clusters using the WISE data. There are more than two thousand star clusters in the current catalogs of star clusters in the Milky Way Galaxy. However, there are still numerous star clusters remaining to be discovered, especially, along the Milky Way. The WISE, NIR to MIR all sky survey, is an efficient source to find star clusters obscured by dust along the Milky Way. Taking the advantage of the power of WISE, we survey a wide area at
${\mid}l{\mid} < 30^{\circ}$ and${\mid}b{\mid} < 6^{\circ}$ , toward to the central region of the Milky Way to find new star clusters. To find cluster candidates, we used two kinds of method: the visual inspection and the brightness density investigation. We will report the progress of this survey. -
We present a comprehensive re-analysis of stellar photometric variability in the field of open cluster M37, using our new high-precision light curves. This dataset provides a rare opportunity to explore different types of variability between short (-minutes) and long (-one month) time-scales. To investigate the variability properties of -30,000 objects, we developed new algorithms for detecting periodic, aperiodic, and sporadic variability in their light curves. About 7.5% (2,284) of the total sample exhibits convincing variations that are induced by flares, pulsations, eclipses, starspots and, in some cases, unknown causes. The benefits of our new photometry and analysis package are evident. The discovery rate of new variables is increased by 63% in comparison with the existing catalog of variables, and 51 previously identified variables were found to be false positives resulting from time-dependent systematic effects. Based on extended and improved catalog of variables, we will review the basic properties (e.g., periodicity, amplitude, type) of the variability and how different they are for different spectral types and for cluster memberships.
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Wilson and Bappu (1957), for the first time, and other precedent studies (Lutz & Kelker 1975; Pasquini et al. 1988; Dupree & Smith 1995; Wallerwstein et al. 1999; Pace et al. 2003) found a tight correlation (called Wilson-Bappu relationship - WBR) between stellar absolute visual magnitude and the width of the Ca II K line emission feature for late type stars. Here we re-visit WBR to claim that WBR can be an excellent indicator of stellar surface gravity of late type stars as well as a good indicator of distance. We have analyzed 103 high-resolution spectra of G, K and M type stars obtained by UVES and BOES by following the method by Pace et al. (2003) for measuring the widths of Ca II K lines(W). WBR found in our samples is Mv=33.26-17.79logW and the correlation is very tight. In this study, the stellar gravity(log g) has been derived using Kurucz ALAS9 model grid and MOOG code, which can determine
$T_{eff}$ and [M/H] too. -
구경 3.6m의 캐나다-프랑스-하와이 망원경(Canada-France-Hawaii Telescope, CFHT)의 주 초점에 설치된 CFH12K CCD 카메라를 이용하여 늙은 산개성단 NGC 1245와 NGC 2506에 대한 V와 I필터를 이용한 CCD측광을 수행하였다. 관측된 영역은 NGC 1245는 84'
${\times}$ 82', NGC 2506은 42'${\times}$ 81'이고, 한계등급 V${\approx}$ 23등급까지 관측하였다. 이론적인 등연령곡선을 사용하여 NGC 1245와 NGC 2506에 대해 각각 물리량 E(B-V) = 0.2, 0.03, (V-M_V)_0 = 12.5, 12.5, log(age) = 9.0, 9.3으로 구하였다. 이로부터 MV${\approx}$ 10등급까지의 광도함수와 질량함수를 구하였다. NGC 1245와 NGC 2506의 질량함수의 기울기를 각각${\Gamma}$ = -1.26${\pm}$ 0.04,${\Gamma}$ = -1.27${\pm}$ 0.07로 얻었고, 이들의 기울기는 태양부근의 낱별의 질량함수의 기울기에 비해 완만하다. 이는 성단에서 질량이 작은 별들의 질량 증발에 의한 역학적 진화의 효과로 보인다. 본 발표에서는 관측 내용과 그 결과를 소개하고자 한다. -
Sco OB1의 핵심성단 NGC 6231를 호주 Siding Spring 천문대 1m 망원경을 사용하여 -40'
${\times}$ 40' 영역을 관측하였다. 측광자료를 바탕으로 성단의 반경, 성간소광 법칙, 나이 및 초기질량함수를 결정하였다. 성단의 반지름은 구성원의 질량에 상관없이 거의 10' ($R{\approx}4.6pc$ )으로 동일한 값을 보였다. 전체적으로는 정상적인 성간소광 법칙을 따르지만, 성단의 중심으로 갈수로 큰$R_V$ 를 보여주며, 이는 과거에 있었을 것으로 추정되는 초신성의 효과로 추정된다. 질량이 큰 별과 X-선으로 선택된 성단의 전주계열성은 비슷한 평균나이를 보이지만 전주계열성은 훨씬 큰 나이분산을 보였다. 성단전체 초기질량함수의 기울기는 Salpeter 초기질량함수의 기울기와 매우 유사한${\Gamma}$ =-1.1${\pm}$ 0.1을 보였으며, 성단 중심거리에 따른 초기질량함수의 기울기는 -1.0${\pm}$ 0.2에서 -1.8${\pm}$ 0.5까지 체계적으로 변화를 하였다. 질량이 큰 O형 별의 쌍성비율이 중심거리에 따른 변화를 보이지 않음에 비추어 볼 때, NGC 6231의 질량분리 양상은 역학적 진화의 결과가 아니라 원초적 질량분리현상으로 결론을 내릴 수 있다. -
We examine both optical and optical/near-infrared (NIR) color distributions of the globular cluster (GC) system in the core of the Coma cluster of galaxies (Abell 1656), centered on the giant elliptical galaxy NGC 4874, to study how non-linearities in the color-metallicity relations of GC systems in large elliptical galaxies are linked to bimodal optical color distributions. Since optical-NIR color distributions of extragalactic GC systems reflect the underlying features of the metallicity distributions, we also present the color-color relation for this GC system. In order to do this, we combine F160W (
$H_{160}$ ) NIR imaging data acquired with the Wide Field Camera 3 IR Channel (WFC3/IR), newly installed on Hubble Space Telescope (HST), with F475W ($g_{475}$ ) and FF814W ($I_{814}$ ) optical imaging data from the HST Advanced Camera for Surveys (ACS). To quantitatively explain the feature of color distributions, we use the Gaussian Mixture Modeling (GMM) code. Finally, we show the radial distribution of the GCs in the field of NGC 4874. -
We observed selected super cluster regions in M82 with 5'5 arcsec field-of-view using near-IR high resolution echelle spectrometer, IRCS, at the SUBARU 8.2 m telescope. The slit width of 0.15 arcsec makes the high resolution (R
${\approx}$ 20,000) spectra in the H and K bands. In this poster, we present sample spectra of [FeII] lines and ro-vibration lines of$H_2$ which trace ionic shocks in the intercloud regions and molecular shocks. The line widths of$Br{\gamma}$ line are also measured to derive the velocity dispersion within the super star clusters. -
한국천문연구원은 1978년 소백산천문대, 1996년 보현산천문대, 2003년 레몬산 천문대를 완공하면서 한국천문학의 광학-적외선 분야를 선도해 왔다. 그동안 각 천문대에서 사용되어 왔던 관측기기들, 특히 천문연에서 개발된 관측기기의 특징을 소개한다. 또한 현재 개발중인 기기와 미래 계획중인 기기를 소개하면서 한국천문학계의 기기개발 부분이 나아갈 방향을 고찰해 보고자 한다.
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Park, Byeong-Gon;Kim, Yeong-Su;Gyeong, Jae-Man;Cheon, Mu-Yeong;Kim, Sang-Cheol;Yun, Yang-No 62.2
한국천문연구원의 대형광학망원경 개발사업(K-GMT)은 거대마젤란망원경(GMT; Giant Magellan Telescope)의 지분 10% 확보를 목표로 2009년부터 2018년까지 수행하고 있는 사업이다. 2011년 GMT 프로젝트에서는 1세대 후보관측장비 개념설계검토회의 수행, 첫번째 주경 최종 마무리, GMT 핵심연구주제 확정을 위한 활동을 수행하였다. 2012년에는 1세대 관측장비를 공식 선정 및 상세 설계 수행, GMT 자료처리센터 구축에 관한 개념설계, 연말로 예정된 GMT PDR 준비를 시작할 예정이다. 국내 사업에서는 GMT 핵심연구그룹 육성을 위하여 AAT 3.9m, CFHT 3.6m, Magellan 6.5m 망원경 활용 연구를 수행하였고 2012년에는 UKIRT 4m 등을 이용한 연구, 계절학교 개최등의 활동이 예정되어 있다. 부경개발분야에서는 시험모델에 대한 2011년 설계검토 및 제작준비완료검토에 이어 최종 시험을 실시할 예정이며 관측기기개발 분야에서는 GMT 1세대 관측장비 선정이 완료되면 본격적으로 기기개발에 참여할 예정이다. -
Kim, Yeong-Su;Go, Ju-Heon;Jeong, In-U;Yang, Ho-Sun;Kim, Ho-Sang;Lee, Gyeong-Don;An, Hyo-Seong;Cho, Myung;Han, In-U;Cheon, Mu-Yeong;Park, Byeong-Gon;Gyeong, Jae-Man;Yun, Yang-No 63.1
한국천문연구원은 GMT (Giant Magellan Telescope)의 부경 중의 하나인 FSM (Fast Steering Mirror)의 시험모델을 개발 중이다. 구경 1.06m의 반사경을 가공하는 중인데, 뒷면 경량화 가공을 마쳤다. 다음 작업으로 비축 비구면의 앞면을 가공하기 위해 반사경의 지지셀을 제작 중이다. 또한 tip-tilt 제어를 위한 test-bed를 제작하여 스프링과 진공을 이용한 무게 상쇄실험을 마쳤다. 미러 셀을 제작하여 실제 상황과 비슷한 환경에서 시험하고자 한다. 또한 tip-tilt의 최종 성능시험을 위한 장치를 개발하고 있다. 이 발표에서는 FSM 시험모델의 개발 현황에 대해 논한다. -
Gyeong, Jae-Man;Kim, Sang-Cheol;Seon, Gwang-Il;Lee, Chang-Hui;Lee, Jun-Hyeop;Lee, Jae-Jun;Sin, Jong-Ho;Seong, Eon-Chang;Kim, Min-Jin;Lee, Jong-Cheol;Park, Byeong-Gon;Kim, Yeong-Su;Cheon, Mu-Yeong 63.2
한국천문연구원의 대형광학망원경 개발사업(K-GMT)의 세 가지 세부 목표 중 GMT 망원경 건설 후 GMT 망원경 활용 극대화가 그 하나이며 이 목표를 달성하기 위한 두 부류의 큰 활동이 이루어지고 있다. 첫째, 국내 전문가로 구성된 과학.기기 워킹그룹(Science Instrument Working Group)은 한국천문학계 연구역량강화 프로그램을 준비하고 시행하고 있으며 2012년 K-GMT 여름학교를 개최할 예정이다. 둘째, 천문연은 2개의 핵심연구주제를 선정하고 2011년부터 학계와 공동으로 pilot 연구를 수행하고 있다. 이 학연공동연구에서는 AAT를 이용한 남반구 별탄생영역 관측, CFHT를 이용한 은하단/은하군 관측을 수행하였고 2012년엔 UKIRT 망원경을 이용하여 우리은하평면의 [FeII] 서베이 관측 등을 수행할 계획이다. -
Lee, Dae-Hui;Nam, Uk-Won;Park, Yeong-Sik;Mun, Bong-Gon;Park, Gwi-Jong;Jeong, Ung-Seop;Pyo, Jeong-Hyeon;Na, Ja-Gyeong;Han, Jeong-Yeol;Cheon, Mu-Yeong;Kim, Geon-Hui;Yang, Sun-Cheol 64.1
Cosmic Infrared Background Experiment (CIBER)는 적외선 카메라 및 분광기를 NASA Sounding Rocket에 탑재, 발사하여 적외선우주배경복사를 관측하는 과제이다. CIBER1은 2006년 NASA의 공식 과제로 승인되어, 미국의 Caltech, 한국의 KASI, 일본의 ISAS/JAXA가 국제협력으로 진행되었으며, 2009년 2월 25일, 2010년 7월 10일, 그리고 2012년 2월 25일에 미국 화이트샌드 미사일 기지에서 NASA 사운딩 로켓에 의해 성공적으로 발사되어 우주관측에 성공하였다. CIBER2는 CIBER1 보다 약 10 배 이상의 성능을 가지는 적외선카메라로써 한국의 KASI는 CIBER2 개발에서 광학계 및 광기계부 개발, 전자부 개발에 참여하고 있다. CIBER2는 2012년에 개발을 시작하여 2013년과 2014년에 각각 발사될 예정이다. -
Jeong, Woong-Seob;Matsumoto, Toshio;Lee, Dae-Hee;Pyo, Jeong-Hyun;Park, Sung-Joon;Moon, Bong-Kon;Ree, Chang-Hee;Park, Young-Sik;Han, Won-Yong;Lee, Hyung-Mok;Im, Myung-Shin;SPICA/FPC Team, SPICA/FPC Team 64.2
The SPICA (SPace Infrared Telescope for Cosmology & Astrophysics) project is a next-generation infrared space telescope optimized for mid- and far-infrared observation with a cryogenically cooled 3m-class telescope. It will achieve the high resolution as well as the unprecedented sensitivity from mid to far-infrared range. The FPC (Focal Plane Camera) is a Korean-led near-infrared instrument as an international collaboration. The FPC-S and FPC-G are responsible for the scientific observation in the near-infrared and the fine guiding, respectively. The FPC-G will significantly reduce the alignement and random pointing error through the observation of guiding stars in the focal plane. We analyzed the pointing requirement from the focal plane instruments. The feasibility study was performed to achieve the requirements. Here, we present the role of SPICA/FPC as a fine guiding camera. -
Han, Won-Yong;Lee, Dae-Hee;Park, Young-Sik;Jeong, Woong-Seob;Moon, Bong-Kon;Park, Kwi-Jong;Park, Sung-Joon;Pyo, Jeong-Hyun;Lee, Duk-Hang;Nam, Uk-Won;Park, Jang-Hyun;Seon, Kwang-Il;Yang, Sun-Choel;Park, Jong-Oh;Rhee, Seung-Wu;Lee, Hyung-Mok;Matsumoto, Toshio 65.1
MIRIS (Multipurpose Infra-Red Imaging System) is the first Korean Infrared Space Telescope developed by KASI (Korea Astronomy and Space Science Institute), and is the main payload of STSAT-3 (Science and Technology Satellite-3). The FM (fight model) of MIRIS has been recently completed, and various performance tests have been made to measure system parameters such as readout noise, system gain, linearity, and dark current. Final thermal-vacumm test of the MIRIS and the vibration test of the electronics box have been performed. Band response tests showed good agreement with the initial design requirements. No significant dark difference was measured within the expected temperature variation range during observation in orbit. Using Pa-alpha band from a uniform source, the readout noise and system gain were measured by mean variance test. To obtain uniform flat image, flat fielding tests were made for each band, and the data will be compared to that obtained in orbit for calibration. The final version of MIRIS FM will be delivered in March, and it will be integrated into the satellite system for the AIT (Assembly Integration, Test) procedure. The launch of MIRIS is expected in November 2012. -
Chung, Hyun-Soo;Je, Do-Heung;Oh, Se-Jin;Roh, Duk-Gyoo;Sohn, Bong-Won;Lee, Sang-Sung;Kim, Hyo-Ryoung 65.2
세계전파통신회의 (WRC; World Radiocommunication Conference)회의는 국제전기통신연합 (ITU)에서 규정하는 국제 전파법 제개정을 위해, 3-4년 간격으로 개최되는 전파통신 관련 최고회의라고 할 수 있다. WRC-12회의는 2012년 1월 23일 - 2월 17일에 걸쳐 스위스 제네바에서 WRC-07회의가 개최되었다. 본 회의에서는 전세계의 국가별 전파사용을 둘러싼 정치적, 경제적 이권 다툼이 치열하게 진행되었으며, 25개의 WRC 의제들에 대해 국제전기통신 연합 산하의 연구반 (ITU-R Study Group)의 연구결과를 토대로 관련 국제전파규약들을 최종적으로 개정하였다. 따라서 국내 전파천문대의 입장에서는 상기 회의의 의제 가운데 국내전파천문대의 원활한 운용과 사용주파수 대역의 보호를 위해 필요한 우리나라의 기고서를 발표하였다. 그 결과 국내의 전파천문대 운영과 관련된 22 GHz 대역이라든지 ALMA용의 275GHz 이상 대역, 달탐사용의 37GHz 대역 등에 대한 신규주파수 또는 보호조건 강화 등이 완료되었다. 본 발표에서는 WRC-12회의에서 결정된 최종결과 및 이들이 국내전파천문대의 향후 운영에 미치는 영향을 보고하고자 한다. 또한 차기 WRC-15회의를 위해 새로 제정된 의제들 가운데 전파천문을 비롯한 과학업무 관련 의제 소개 및 대응책 검토를 하고자 한다. -
Lee, Jung-Won;Wang, Ming-Jye;Kim, Soo-Yeon;Li, Chao-Te;Chen, Tse-Jun;Kang, Yong-Woo;Lu, Wei-Chun;Shi, Sheng-Cai;Han, Seog-Tae 66.1
We have developed superconducting mixer receivers for 129 GHz VLBI observation in Korean VLBI Network(KVN). The developed mixer has a radial waveguide probe with simple transmission line LC transformer as a tuning circuit to its 5 series-connected junctions, which can have 125-165 GHz as operation RF frequency. For IF signal path a high impedance quarter-wavelength line connects the probe to one end of symmetric RF chokes. DSB receiver noise of the mixer was about 40 K over 4-6 GHz IF band whereas we achieved about uncorrected SSB noise temperature of 70 K and better than 10 dB IRR in 2SB configuration with 8-10 GHz IF band. Insert-type receiver cartridges using the mixers have been assembled for all three KVN stations. On-site performance summary in commissioning phase is presented. -
Building a relativistic magnetohydrodynamic (RMHD) code based on upwind scheme is a challenging project, because eigenvalues and eigenvectors are not yet analytically given. Here, we present analytic expressions for eigenvalues and eigenvectors in isothermal flows. And then we show tests performed with a code based on the total variation diminishing (TVD) scheme.
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Shocks are evolved when the relativistic jets in active galactic nuclei (AGNs), black hole binaries, supernova remnants (SNR) and gamma-ray bursts (GRBs) interact with the surrounding medium. The high energy particles are believed to be accelerated by the diffusive shock acceleration and the strong magnetic field is generated by Weibel instability in the shock. When ultrarelativistic electrons with strong magnetic field cool by the synchrotron emission, the radiation is observed in gamma-ray burst and the near-equipartitioned magnetic field in the external shock delays the afterglow emission. In this paper, we performed the 3D particle-in-cell (PIC) simulations to understand the characteristics of these relativistic shock and particle acceleration. Forward and reverse shocks are shaped while the unmagnetized injecting jet interacts with the unmagnetized ambient medium. Both upstream and downstream become thermalized and the particle accelerations are shown in each transition region of the shock structures.
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Lee, Yong-Seok;Kim, Tae-Yeon;Yu, Je-Geon;Jin, Ho;Seon, Jong-Ho;Lee, Dong-Hun;Imme, Thomas;Lin, Robert P. 67.2
경희대학교와 UC Berkeley, Imperial College London은 우주관측을 위한 초소형 인공위성인 TRIO-CINEMA(TRIO-CINEMA) Project를 수행하고 있다. TRIO-CINEMA는 총 3기의 인공위성으로 경희대학교에서 2기의 위성을, UC Berkeley에서 1기의 위성을, Imperial College에서 3개의 자력계를 제작하고 있다. CINEMA는 Cubesat의 3U 규격으로 크기는$100mm{\times}100mm{\times}340.5mm$ 이고 무게는 약 3 kg, 소비전력은 약 3 W이며, 지구 주변의 ENA측정을 위한 주 탑재체인 STEIN(SupraThermal Electrons, Ions, and Neutrals)과 자기장 측정을 위한 부 탑재체인 MAGIC(MAGnetometer from Imperial College)이 탑재되어 약 1년간 800 km 태양동주기 궤도에서 임무를 수행할 예정이다. 위성의 발사는 별도의 POD(Picosatellite Orbital Deployer)라는 Adaptor를 사용해 발사체에 탑재되는데, 발사환경에서 위성이 받을 모든 현상에 관하여 NX Nastran을 사용해 계산을 진행하였다. 계산 결과의 검증을 위해 위성의 Structure Model을 가지고 Random Vibration test를 수행해 위성의 고유 진동수를 측정하였다. 또한 위성이 궤도에서 운용 중 다양하게 받게 되는 열원에 따른 위성의 각 부분의 온도변화를 NX TMG program을 사용하여 계산하였다. 계산 결과의 검증을 위해 3월 Thermal Cycle test 및 Thermal Balance test를 수행할 예정이다. UC Berkeley에서 제작한 위성 1기는 제작완료 후 발사를 위해 발사장으로 배송을 완료하였고, 경희대학교에서 제작 중인 CINEMA 위성 2기는 2012년 후반기 러시아에서 Dnepr 로켓을 사용해 발사 예정이다. -
CIBER 2(Cosmic Infrared Background ExpeRiment 2)는 CIBER1의 후속과제로 진행되는 사업으로써 적외선 기기를 NASA Sounding Rocket에 탑재하여 0.5-2.1
${\mu}m$ 파장대의 적외선 우주배경복사를 관측하고 실험하는 과제이다. CIBER 2는 NASA에서 공식 승인되어 진행되고 있는 사업이며, 미국의 Caltech, 한국의 KASI, 일본의 ISAS/JAXA가 국제협력으로 진행하는 과제이다. 한국의 KASI는 반사경의 광학계 및 광기계부 개발, 전자부 개발에 참여하고 있다. CIBER 2의 광학계는 카세그레인 방식으로써 주경의 직경은 300mm이다. CIBER 2는 77K로 냉각되어 적외선우주배경복사를 관측하기 때문에 특히, 열수축에 의한 영향을 고려하여 설계, 제작, 조립이 되어야 한다. 또한, 광학계 구조물이 조립되는 로켓의 내경이 400mm이기 때문에 광학계 구조물의 직경에 제한이 따른다. 본 발표에서는 KASI가 주도적으로 개발 중인 반사경 마운트와 광학계 구조물의 초기설계와 광기계 해석결과들에 대해서 논한다. -
Gang, Yong-U;Lee, Jeong-Won;Han, Seok-Tae;Wi, Seok-O;Je, Do-Heung;Kim, Su-Yeon;Song, Min-Gyu;Jeong, Mun-Hui;Gang, Ji-Man 68.2
한국우주전파관측망(KVN)을 이루는 각 망원경에 22GHz, 43GHz, 86GHz, 129GHz의 4개의 주파수 대역을 동시에 관측할 수 있는 전파 수신시스템을 구축하고 있다. 현재, 22GHz와 43GHz의 수신기가 설치되어 있고, 86GHz와 129GHz 수신기가 2012년 상반기에 설치 완료할 예정이다. 이들 중, 129GHz 수신기의 핵심인 초전도 전파수신소자에 공급하는 바이어스 전원의 공급 시스템을 2년에 걸쳐 설계 및 제작 완료하였다. 개발된 Bias Supply System은 주 보드, User Interface, 전용 정전압 모듈, Protection 모듈 등이 한 Sub-Rack에 결합되어 있다. 먼저, Bias Supply System 시제품 1set를 우선 제작하여 연세전파천문대의 129GHz수신기 초전도 전파수신소자 제어에 설제 적용하였다. 이를 바탕으로, 수정과 보완 및 Remote M&C 기능을 추가하여 새로 설계하고 제작한 최종 Bias Supply System 3set를 개발 완료하였고, 129GHz 수신기 3기의 초전도 전파수신소자 구동에 운용하고 있다. 본 발표에서는 그 개발 내용을 소개하고자 한다. -
Monte Carlo codes for extensive air shower (EAS) simulate the development of EASs initiated in the Earth's atmosphere by ultra-high energy cosmic rays (UHECRs) with energy exceeding -
$10^{18}$ eV. Here, we compare EAS simulations with two different codes, CORSIKA and COSMOS, presenting quantities including the longitudinal distribution of particles, depth of shower maximum, kinetic energy distribution of particle at the ground, and calorimetric energy. In addition, the lateral distribution of local energy density far from the EAS core has been known as an important quantity to estimate the energy of UHECRs. We also present the lateral distribution function obtained from GEANT4 simulations for detector response. -
O, Se-Jin;Yeom, Jae-Hwan;No, Deok-Gyu;O, Chung-Sik;Jeong, Jin-Seung;Jeong, Dong-Gyu;Atsush, Miyazaki;Tomoaki, Oyama;Noriyuki, Kawaguchi;Hideyuki, Kobayashi;Kensuke, Ozeki;Hirofumi, Onuki 69.2
한국천문연구원과 일본국립천문대는 2006년부터 한일공동으로 한일공동VLBI상관기(KJJVC)를 개발하였다. 한일상관센터(KJCC)에 각 구성시스템을 설치한 후 최근까지 시험운영을 수행하였으나 한일공동VLBI상관기의 핵심인 VLBI상관서브시스템(VCS)에서 프린지회전 모듈이 정상적으로 동작하지 않는 것을 발견하여, 일본국립천문대 및 제작사와 함께 이 문제를 해결하였다. 프린지 회전모듈의 문제점은 상관결과를 AIPS 등에서 분석하면, Fringe fitting후에 Cross-power spectrum의 진폭과 위상성분이 고주파 영역에서 감쇠하는 현상이다. 본 발표에서는 VCS 프린지 회전모듈의 문제점 해결과 KJJVC를 구성하는 각 구성시스템의 현황, 그리고 운영에 대해 간략히 기술한다. -
CQUEAN (Camera for QUasars in EArly uNiverse)은 초기우주천체 연구단(Center for Exploration of Origin of the Universe) 사업에서 개발한 CCD 카메라로서 초기우주의 퀘이사 후보를 찾기 위한 목적으로 설계되었다. CCD를 구동할 때는 픽셀 다이오드의 PN 접합층에 공핍층(depletion layer)을 생성하기위해 역 바이어스 전압을 준다. 이 전압에 의해 CCD를 사용한 관측 시 광이온화와 열이온화 현상에 의해 생성된 전자의 전하값에 추가로 바이어스 값이 읽혀진다. 정확한 CCD 측광 결과를 얻어내기 위해서는 안정된 바이어스를 유지해야 한다. 본 연구에서는 향후 CQUEAN의 보다 정확한 관측 및 데이터 처리에 대비하여 CQUEAN의 바이어스 특성을 분석하여 이 값에 영향을 주는 요인을 찾고 해결책을 논의한다.
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The night sky in Mongolia is known to be one of the darkest and clearest in Asia. The seasonal dust winds from the Gobi desert, however, might degrade the transparency of the night sky and affect the photometrical quality for astronomical research. In this poster, we present the preliminary results of the first transparency measurement of the night sky in Monglia. The observations are done at Zuunmod located at 25 km south from Ulaanbaatar in 2011 October 26-31. We used a CCD camera (QSI 583s) attached to an 80 mm aperture refractor telescope (William Optics Zentih Star 80 II ED APO). A new supernova, SN2011fe, and a young stellar object, HBC 722, were monitored in order to measure the extinction coefficients. These values in Mongolia are compared with those in other astronomical observatory.
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Studying the environments in which core-collapse supernovae (SNe) explode and evolve is essential to establish the nature of the mass loss and the explosion of the progenitor star. The spatial structure of the outer shock in young core-collapse SNR provides an excellent opportunity to study the nature of the medium into which the remnant has been expanding. I will review studies of the outer shocks in young Galactic SNRs using Chandra X-ray observations and discuss the nature of the winds and the progenitor stars.
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We present the results of HI 21 cm line observations to explore the nature of the high-velocity (HV) HI gas at - 173
${\circ}$ , which appears as faint, wing-like, Hi emission that extends to velocities beyond those allowed by Galactic rotation in the low-resolution surveys. We designate this feature as Forbidden Velocity Wing (FVW) 172.8+1.5. Our high-resolution Arecibo HI observations show that FVW 172.8+1.5 is composed of knots, filaments, and ring-like structures distributed over an area of a few degrees in extent. These HV HI emission features are well correlated with the HII complex G173+1.5, which is composed of five Sharpless HII regions distributed along a radio continuum loop of size 4.4${\times}$ 3.4, or -138 pc${\times}$ 107 pc, at a distance of 1.8 kpc. G173+1.5 is one of the largest star-forming regions in the outer Galaxy. The HV HI gas and the radio continuum loop seem to trace an expanding shell. Its derived HI parameters including large expansion velocity (55 km/s) imply the SNR interpretation. Hot xray emission is detected within the HII complex, which also supports its SNR origin. The FVW172.8+1.5 is most likely the products of a supernova explosion(s) within the HII complex, possibly in a cluster that triggered the formation of these HII regions. -
We present the results of dust scattering simulations carried out for the Orion Eridanus Superbubble region by comparing them with observations made in the far-ultraviolet. The albedo and the phase function asymmetry factor (g-factor) of interstellar grains were estimated as well as the distance and thickness of the dust layers. The results are: 0.39-0.45 for the albedo and 0.25-0.65 for the g-factor, in good agreement with previous determinations and theoretical predictions. The distance of the assumed single dust layer, modeled for the Orion Molecular Cloud Complex, was estimated to be -110 pc and the thickness ranged from -130 at the core to -50 pc at the boundary for the region of the present interest, implying that the dust cloud is located in front of the Superbubble. The simulation result also indicates that a thin (-10 pc) dust shell surrounds the inner X-ray cavities of hot gas at a distance of -70-90 pc.
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The far ultraviolet (FUV) wavelength (900-1750A) range includes a wealth of important astrophysical information related to the cooling of hot gas, fluorescent emission from H2 molecules, and starlight scattered off dust particles. Among these, we would like to focus on the scattered emission of the central star by dust with the example of the FUV halo surrounding
${\alpha}$ Vir (Spica). While scattering properties of dust have been studied with the GALEX data, the improved dataset of STSAT-1 revealed many detailed structures of this interesting region. For example, the FUV continuum map obtained from the STSAT-1 observations shows enhanced emission in the southern part of the Spica halo region, where the dust level is also high. In fact, the FUV continuum intensity is seen to have a good correlation with the IRAS 100${\mu}m$ emission data. It is also seen that the scattered spectrum is softer than the original one emitted by the central star, which is attributed to the increase in the dust-scattering albedo with wavelength. We have developed a Monte Carlo code that simulates dust scattering of light including multiple encounters. The code is applied to the present Spica halo region to obtain the scattering properties such as the albedo and the phase function asymmetry factor. -
It is known that the diffuse H
${\alpha}$ halos around bright H II regions are more extended than the dust-scattered halos around point sources and the line ratios [S II]${\lambda}$ 6716/H${\alpha}$ and [N II]${\lambda}$ 6583/H${\alpha}$ observed outside of bright H II regions are generally higher than those in H II regions. These observational facts have been regarded as evidence against the dust-scattering origin of the diffuse H${\alpha}$ emission and the effect of dust-scattering has been neglected in studying the diffuse H${\alpha}$ emission. In this paper, we find, however, that dust-scattered halos of H II regions should be more extended than those of point sources and is in good agreement with the observed H${\alpha}$ profiles around H II regions. We also found that the observed line ratios [S II]/H${\alpha}$ , [N II]/H${\alpha}$ , and He I${\lambda}$ 5876/H${\alpha}$ in the diffuse regions can be well reproduced with the dust-scattered halos around H II regions which are photoionized by late O- and/or early B-type stars in the interstellar medium with the abundances close to those of the warm neutral medium. Therefore, we conclude that the diffuse H${\alpha}$ emission may originate mostly from the dust-scattering. -
Shinn, Jong-Ho;Pyo, Tae-Soo;Lee, Jae-Joon;Lee, Ho-Gyu;Koo, Bon-Chul;Sung, Hwan-Kyung;Moon, Dae-Sik;Kyeong, Jae-Mann;Park, Byeong-Gon 74.2
We present [Fe II] 1.64${\mu}m$ imaging observations for jets and outflows from young stellar objects over the northern part (-24'${\times}$ 45') of the Carina Nebula, a typical evolved massive star forming region. The observations were performed with IRIS2 of Anglo-Autralian Telescope and the seeing was -1.5". Several jets and outflows features are detected at seven different regions, and one new Herbig-Haro Object is identified. The [Fe II] features have knotty and elongated shapes, and distribute around the triangular area formed by the star clusters Tr 14, Tr 15, and Tr 16, which contain many massive stars. The [Fe II] feature shows a highest detection rate (3.2 %) for the earliest stage YSOs, and the rate decreases as the stage evolves. The low detection rate (1.5 %) of [Fe II] features from the numerous YSOs seem to be related with the severe radiation environment of the Carina Nebula. The outflow rate shows reasonable relations with the physical parameters of the corresponding YSOs-derived from the SED fitting-such as the accretion luminosity, the stellar mass, the stellar age, the disk accretion rate, etc. -
Lee, Young-Ung;Kim, Young-Sik;Kang, Hyun-Woo;Jung, Jae-Hoon;Lee, Chang-Hoon;Yim, In-Sung;Kim, Bong-Gyu;Kim, Hyun-Goo;Kim, Kwang-Tae 75.1
We have observed the part of the second quadrant of the Galactic Plane in$^{13}CO(1-0)$ using the multibeam receiver system installed on the 14 m telescope at Taeduk Radio Astronomy Observatory. The target region (L=108 to 112.5) is the part of the$^{12}CO$ Outer Galactic Plane Survey (Heyer et al. 1998), and it is for the exact Galactic plane with the latitude range of +1 and -1 degree. Total of 48,000 spectra (about 9 square degees) were obtained on 50" grid. The selected velocity resolution is 0.63 km/sec and sensitivity per channel is 0.17 K, and the covered velocity is 320 km/sec. We developed a new reduction method, which effectively deals with a relatively noisy 3-dimensional database. The collected$^{13}CO$ database will be manipulated with pre-existing$^{12}CO$ data to get several physical parameters. As it is located in the second quadrant, the kinematic distances of the individual clouds, which will be identified, can be estimated relatively easily without any distance ambiguity. In this meeting we present the reduction method, statistics, and some channel maps, integrated intensity maps, and spatial-velocity maps. We intend to clarify any difference of their characteristics between the clouds in the Outer Galaxy and Inner Galaxy using our data base. -
Turbulence is ubiquitous in astrophysical fluids such as the interstellar medium and intracluster medium. To maintain turbulent motion, energy must be injected into the fluids. In turbulence studies, it is customary to assume that the fluid is driven on a scale, but there can be many different driving mechanisms that act on different scales in astrophysical fluids. We expect different statistical properties of turbulence between turbulence with single driving scale and turbulence with double driving scales. In this work, we perform 3-dimensional incompressible MHD turbulence simulations with energy injection in two ranges, 2
${\surd}$12 (large scale) and 15 One of the main challenges for future 21-cm observations is to remove foregrounds which are several orders of magnitude more intense than the HI signal. We propose a new technique for removing foregrounds of the redshifted 21-cm observations. We consider multi-frequency interferometer observations. We assume that the 21-cm signals in different frequency channels are uncorrelated and the foreground signals change slowly as a function of frequency. When we add the visibilities of all channels, the foreground signals increase roughly by a factor of N because they are highly correlated. However, the 21-cm signals increase by a factor of sqrt{N} because the signals in different channels contribute randomly. This enables us to obtain an accurate shape of the foreground angular power spectrum. Then, we obtain the 21-cm power spectrum by subtracting the foreground power spectrum obtained this way. We describe how to obtain the average power spectrum of the 21-cm signal.The understanding spectral characterization of possible earth-like extra solar planets has generated wide interested in astronomy and space science. The technical central issue in observation of exoplanet is deconvolution of the temporally and disk-averaged spectra of the exoplanets. The earth model based on atmospheric radiative transfer method has been studied in recent years for solutions of characterization of earthlike exoplanet. In this study, we report on the current progress of the new method of 3D earth model as a habitable exoplanet. The computational model has 3 components 1) the sun model, 2) an integrated earth BRDF (Bi-directional Reflectance Distribution Function) model (Atmosphere, Land and Ocean) and 3) instrument model combined in ray tracing computation. The ray characteristics such as radiative power and direction are altered as they experience reflection, refraction, transmission, absorption and scattering from encountering with each all of optical surfaces. The Land BRDF characteristics are defined by the semi-empirical "parametric-kernel-method" from POLDER missions from CNES. The ocean BRDF is defined for sea-ice cap structure and for the sea water optical model, considering sun-glint scattering. The input cloud-free atmosphere model consists of 1 layers with vertical profiles of absorption and aerosol scattering combined Rayleigh scattering and its input characteristics using the NEWS product in NASA data and spectral SMARTS from NREL and 6SV from Vermote E. The trial simulation runs result in phase dependent disk-averaged spectra and light-curves of a virtual exoplanet using 3D earth model.We present high-resolution radial velocity measurements of K2 giant${\varepsilon}$ CrB from February 2005 to January 2012 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph at Bohyunsan Optical Astronomy Observatory. We find that the RV measurements for${\varepsilon}$ CrB exhibit a periodic variation of 418 days with a semi-amplitude of 129 m/s. There is no correlation with RV measurements and inhomogeneous surface features by examining chromospheric activity indicator (Ca II H region), the Hipparcos photometry, and bisector velocity span. Thus, Keplerian motion is the most likely explanation, which suggests that the RV variations arise from an orbital motion. Assuming a possible stellar mass of 1.7$M_{\odot}$ , for${\varepsilon}$ CrB, we obtain a minimum mass for the planetary companion of 6.7$M_{Jup}$ with an orbital semi-major axis of 1.3 AU, and an eccentricity of 0.11. We support that more massive stars harbor more massive planetary companions in giant hosting planetary companions (Dollinger et al. 2009), as well as, we discuss the frequency of detected planetary companions with the metallicity distribution in giant (Pasquini et al. 2007; Quirrenbach et al. 2011).Infrared dark clouds(IRDCs) are believed to be the progenitors of massive stars and clusters. We obtained 350 and 850${\mu}m$ continuum maps of the IRDC G049.40-00.01 using SHARC-II on CSO. Twenty-one dense clumps were identified within G049.40-00.01 based on the 350${\mu}m$ continuum map with an angular resolution of about 9.6". We present submillimeter continuum maps and report physical properties of the clumps. The masses of clumps are from 50 to 600 solar mass. About 70% of the clumps are associated with bright 24${\mu}m$ emission sources indicating protostars. The most massive two clumps show enhanced, extended 4.5${\mu}m$ emission representing on-going star forming activity. The size-mass distribution of the clumps suggests that many of them are forming high-mass stars. G049.40-00.01 contains numerous objects in various evolutionary stages of star formation, from pre-stellar clumps to H II regions.We present near-IR imaging polarimetry of the 5${\times}$ 9 fields (-39'${\times}$ 69') centered at 30 Doradus in the Large Magellanic Cloud (LMC), using the InfraRed Survey Facility (IRSF). We obtained polarimetry data in J, H, and Ks bands using the JHKs-simultaneous imaging polarimeter SIRPOL in 2008 December and 2011 December. We measured Stokes parameters of point-like sources to derive the degree of polarization and the polarization position angle. Since our results are suffered from non-photometric weather, we compare the polarization results from 2008 and those from 2011, and examine the photometric reliabilities between the two runs. Our survey data will be compared with molecular and dust maps to reveal the large-scale magnetic field properties in the star-forming clouds.Orion A 분자운은 별탄생이 활발하게 일어나는 영역이면서 태양계에 비교적 가깝다. 그렇기 때문에 낮은 분해능으로도 자세한 관측이 가능하다. Orion A 분자운까지의 거리가 450 pc 이므로 대덕전파안테나 1' beam으로 0.13 pc 가 된다. 이곳에는 필라멘트 구조가 있는데 FCRAO를 통한 다파장관측을 통해서 필라멘트 구조가 확인되었다.(Melnick et al. 2011). 필라멘트는 길이 4.8 pc, 너비 1.5 pc 로 대덕전파망원경의 1' beam으로 자세한 관측이 가능하였다. 2010년 11월-2011년 5월까지 Orion A 분자운을 대덕전파망원경을 이용하여$^{12}CO$ ,$^{13}CO$ (J=1-0) 분자선 관측을 하였으며, 관측영역은 적경: 5h 32m - 5h 37m, 적위:$-5^{\circ}$ 14' -$-5^{\circ}$ 37'으로 ($1^{\circ}{\times}1^{\circ}$ ) 영역을 관측하였다. 그 결과 필라멘트구조를 확인할 수 있었으며 일자 형태로 분포되어 있다는 구조적 결과 얻었다. 관측된 필라멘트 덩어리의 전형적인 크기는 약 0.7 pc, 밀도는 약$10^4cm^{-3}$ , 질량은 약 500$M_{\odot}$ 이다. 매우 밀한 곳은 1000 M${\bigodot}$ 이상의 질량분포도 나타내고 있다. 이것은 이 지역이 일반적인 분자운과 비교했을 때 고밀도 영역임을 나타내고 있다. 더욱 자세한 밀도구조와 질량분포를 밝혀보고 별탄생과의 관련성을 연구하고자 한다.We present here$UBVI$ and H${\alpha}$ photometric results of stellar sources in the bubble nebula NGC 7635. The early type members are selected from the photometric membership criteria. H${\alpha}$ photometry allows us to detect 11 pre-main sequence candidates with H${\alpha}$ emission. In addition, we performed PSF photometry for the Spitzer IRAC and MIPS 24${\mu}m$ images from archive (program ID 20726, PI: J. Hester) in order to search for the young stellar objects (YSOs). Total 19 sources are classified as YSOs (7 class I, 11 class II, and 1 transitional disk candidates) in the color-color diagrams according to the classification scheme of Gutermuth et al.. Among them, 7 YSOs have counterparts in optical photometric data. These stars can be divided into two groups at given color indices. It implies that there occurred the star formation events more than twice. We would like to discuss the star formation history in the bubble nebula using the results from SED fitter (Robitaille et al.), color composite image from IRAC bands, and spatial distribution of early type stars and YSOs.This study is aim to understand the distribution and the property of LISM (local interstellar medium) using the high resolution spectra of the 26 early type stars in the five open clusters ( IC 4665, Stephenson 1, Collinder 359, Roslund 5 and Collinder 70). These spectra have been observed by BOES in Bohyunsan observatory from 2009 November to 2011 Feburary, of which resolution is 45,000. We used IRAF for the data reduction (Bias subtraction, Flat-field division, and wavelength calibration) and DECH for the deriving the equivalent widths of 4 interstellar lines - Ca II K (3934${\AA}$ ), Na I D (5890, 5896${\AA}$ ) and K I (7698${\AA}$ ) and the column densities of those elements in LISM toward the clusters. The results of this study provide clues for better understanding of the LISM toward these clusters.NGC 6803 is an elliptical ring shape planetary nebula. We analyzed the high dispersion spectra which had been observed with the Hamilton Echelle Spectrograph attached to the 3-m Shane telescope of Lick Observatory. We also investigated the low dispersion UV spectral data obtained with the 60-cm interstellar ultraviolet explorer. Diverse excitation lines were found from neutral to quadruply ionized ions. The temperature diagnostic lines indicate relatively low electron temperatures, i.e.,$T_{\epsilon}{\leq}9500$ K for most lines except for [ClIV] - 11,500 K. In spite of its simplistic bi-laterally symmetrical elliptical shape, the nebula appears to be very complex of a hugh density range from 1300 to 80,000$cm^3$ . A comparison of the two epoch data suggests that the density increase occurred in the high excitation line zone near the inner boundary. We derived the chemical abundances of He, C, N, O, Ne, S, Ar, Cl, and K. The chemical abundances of NGC 6803 are enhanced compared with the average Galactic planetary nebula. Our self-consistent photo-ionization model study implies that the effective temperature of the central star is 90,000 K and its luminosity is 2400$L_{\odot}$ . The evolutionary track suggests that the progenitor of NGC 6803 was about 0.9 -- 1.0$M_{\odot}$ star, which might be born from a metal-rich zone near the galactic disk, but now relocated into the present high Galactic latitude.We firstly present the unified Far-UV continuum map of the Taurus-Auriga-Perseus (TPA) complex, one of the largest local associations of dark cloud located in (l, b)=([152,180], [-28, 0]), by merging both FIMS and GALEX. The FUV continuum map shows that dust extinction correlate well with the FUV around the complex. It says strong absorption in the dense Taurus cloud and Auriga cloud. Although the column density of Perseus and California cloud is similar to Taurus' and Auriga's, Perseus and California cloud do not show strong absorption in FUV because they are more distant than Taurus and Auriga cloud. We also present the dust scattering simulation based on Monte Carlo Radiative Transfer technique. Through the result of Monte-Carlo dust scattering simulation and comparing the result with FIMS-GALEX unified map we gain deeper understanding related to the spatial dust distribution of TPA region. As a preliminary result of the simulation we present the most probable front face, thickness, albedo, and asymmetry factor in this region, respectively. Through this work we can show a certain inclination of the spatial dust distribution. During this study we have developed the FUV dust scattering simulation code using Monte-Carlo method. We expect that it will be generally used to simulate dust scattering in the Galaxy.Herschel Key Program 중의 하나인 "Dust, Ice and Gas In Time (DIGIT)"의 관측 및 분석결과를 발표하고자 한다. 특히 DIGIT 천체들 중 Photodetector Array Camera and Spectrometer (PACS)로 관측된 별생성 초기 단계에 있는 embedded objects들의 FIR SED와 CO,$H_2O$ , OH, [OI], [CII]의 FIR 천이선들의 공간분포와 생성기작을 분석한다. 뿐만 아니라, 원시성의 특성들($L_{bol}$ 과$T_{bol}$ )과 이들 각 분자/원자선에 의한 냉각률의 관계를 통계적으로 분석한 결과를 제시한다.Kim, Kee-Tae;Byun, Do-Young;Jung, Tae-Hyun;Kim, Jong-Soo;Kim, Mi-Kyung;Hirota, Tomoya;Sugiyama, Koichiro;Honma, Mreki;KVN+VERA Star Formation Working Group, KVN+VERA Star Formation Working Group 81.2
Using KVN we made a fringe survey of 44GHz Class I CH3OH maser sources, which have not detected by any VLBI facility. We will present the results and discuss the implications.Kim, Mi-Ryang;Lee, Chang-Won;Kim, Gwan-Jeong;Dunham, M.;Allen, L.;Myers, Philip C.;Evans, N. 82.1
We present results of searching for the Very Low Luminosity Objects (VeLLOs; internal luminosity Lint<0.1Lo) candidates in the Gould Belt's clouds using infrared observations from 3.6 to 70 micron by the Spitzer Space Telescope. More than 100 VeLLO candidates were selected through the criteria by Dunham et al. and our additional ones. The candidates in Northern sky were recently observed with high density tracers such as N2H+ (1-0) and HCN (1-0) using Korea VLBI Network (KVN) 21m telescope at Yonsei site to check their embeddedness in dense gas envelopes. A total of 25 out of 74 VeLLO candidates were detected in either N2H+ or HCN (1-0) line while 9 candidates were detected in both tracers. These are more likely bona fide VeLLOs which need to be studied further in future. In this study the bolometric luminosities for 40 VeLLOs (25 from this study and 15 from Dunham et al.) were estimated and found to be significantly smaller than those given by various theoretical model tracks with constant accretion rate in a BLT diagram, indicating the constant accretion process suggested by standard star formation models can not explain the faintness of the VeLLOs. In the talk we will discuss on some possible explanation of why the VeLLOs are faint.We present Herschel-PACS observations of L1448-MM, a Class 0 protostar with a prominent outflow, part of the DIGIT Key Program (PI: N. Evans). We detect numerous emission lines including CO and$H_2O$ rotational transitions, OH transitions, and [OI] forbidden transitions at wavelengths from 55 to 210${\mu}m$ . The$H_2O$ , [OI], mid-J CO (J < 23), and OH emission distributes along the outflow direction although high-J CO and other OH emission peaks at the central spatial pixel. According to our simple excitation analysis, CO seems to have two temperature components of warm and hot, which might be attributed to the PDR and shock, respectively. After exploring a wide range of physical conditions with a non-LTE LVG code, RADEX, we found that either shock alone or the combination of PDR and shock can explain the observations. The relative fraction of observed line luminosities suggest that L1448-MM is shielded from the UV radiation because$H_2O$ and CO are the dominant coolants rather than OH and [OI]. In addition, our observed fluxes match better with C-shock models rather than J-shocks. The non-LTE LVG model supports that the IR pumping process is important for OH transitions because the OH line ratios are fitted much better when the dust thermal continuum is included.We have developed an self-consistent PDR model to synthesize warm CO lines of Herschel/PACS observations more accurately. The PDR model solves the FUV continuum radiative transfer, gas energetics, and chemistry simultaneously. A local FUV radiation flux is calculated by using a Monte Carlo method taking anisotropic scattering into account. A new (r,${\delta}$ ) coordinate system was used, where the r is the distance from the origin and the${\delta}$ is z/$R^2$ in the cylindrical coordinate of (R,z). This is an adequate coordinate system to represent a power-law density of an envelope and a high spatial resolution near the outflow wall. The gas enegetics and chemistry are solved locally and considered$10^4K$ blackbody radiation field instead of the interstellar radiation filed. This newly developed model can be used to analyze quantitatively the effect of UV-heated outflow walls on the warm molecular lines in the embedded proto-stellar objects.We have carried out simultaneous 22GHz$H_2O$ and 44GHz Class I$CH_3OH$ maser survey of 112 ultra-compact HII regions (UCHIIs) twice in 2010 and 2011. We detected$H_2O$ maser and$CH_3OH$ maser emission from 76(68%) and 49(44%) UCHIIs, respectively. Among them 15$H_2O$ masers and 32$CH_3OH$ masers are new detections. These high detection rates suggest that the occurrence periods of both masers are significantly overlapped with the UCHII phase.$CH_3OH$ masers always have small (<10 km s-1) relative velocities with respect to the natal molecular cores, while$H_2O$ masers often show larger velocities. We find 20 UCHIIs with$H_2O$ maser lines at relative velocities >30 km s-1. The formation and disappearance of$H_2O$ masers is frequent over one-year time interval. In contrast,$CH_3OH$ masers usually do not show substantial variation in intensity, velocity, or shape. The isotropic luminosities of both masers well correlate with the bolometric luminosities of the central stars when data points of lowand intermediate-mass protostars are added:$L_{H_2O}=5.89{\times}10^{-9}{(L_{bol})^{0.69}}$ and$L_{CH_3OH}=4.27{\times}10^{-9}{(L_{bol})^{0.62}}$ . They also tend to increase with the 2cm radio continuum luminosity of UCHIIs and the 850 um continuum luminosity of the associated molecular cores. We discuss some individual sources.Recent spectropolarimetric observations with high spatial resolution and high polarization sensitivity have provided us with new insight to better understand the quiet-Sun magnetism. This talk is concerned with the ubiquitous transient horizontal magnetic fields in the quiet-Sun, as revealed by the Solar Optical Telescope (SOT) on board Hinode satellite. Exploiting the SOT data with careful treatment of photon noise, we reveal the enigmatic properties of these horizontal magnetic fields such as lifetime, size, position in terms of granular structure, occurrence rate, three-dimensional structure, total magnetic flux, field strength distribution, relationship with the meso- and super-granulations and so on. Based on these observational consequences, we conjecture that the local dynamo process, which takes place in a relatively shallow layer with the granular size, produces these transient horizontal magnetic fields and that these horizontal magnetic fields contribute to the considerable amount of quiet-Sun magnetic fields. We also estimate the magnetic energy flux carried by these horizontal magnetic fields based on the statistical data, and find that the total magnetic energy is comparable to the total chromospheric and coronal energy loss, implying their important role for the chromospheric heating and dynamism.We studied the controlling parameters of flux emergence with a focus on the relation between the configuration of coronal magnetic field and the pre-emeged state of subsurface magnetic field. We performed a series of magnetohydrodynamic simulations (dynamic model) and find an interesting result on the twist of coronal magnetic field, that is, the coronal magnetic field formed via flux emergence actually contains less amount of twist (relative magnetic helicity normalized by magnetic flux) than what is expected in kinematic models for global-scale solar eruptions. Based on this result, we propose another possible mechanism for producing these global-scale solar eruptions.In this study we use three-dimensional magnetohydrodynamic simulations of flux emergence from solar subsurface layer to corona. In order to study the twist parameter of magnetic field we compare the simulations for strongly twisted and weakly twisted cases. Based on the results, we derive a flux expansion factor of selected flux tubes which is a ratio of expanded cross section to the one measured at the footpoint of the flux tube. To understand the effect of flux expansion factor, we make a comparison between magnetic field configuration and the expansion factor. By using a fitting function of hyperbolic tangent we derive noticeable correlations among the strength of the vertical magnetic field, current density and expansion factor. We discuss what these results tell about the relationship between the twist of emerging field and the mechanism for the solar wind.In this paper, we introduce the 3D modeling of the coronal magnetic field in the solar active region by extrapolating from the 2D observational data numerically. First, we introduce a nonlinear force-free field (NLFFF) extrapolation code based on the MHD-like relaxation method implementing the cleaning a numerical error for Div B proposed by Dedner et al. 2002 and the multi-grid method. We are able to reconstruct the ideal force-free field, which was introduced by Low & Lou (1990), in high accuracy and achieve the faster speed in the high-resolution calculation (512^3 grids). Next we applied our NLFFF extrapolation to the solar active region NOAA 10930. First of all, we compare the 3D NLFFF with the flare ribbons of Ca II images observed by the Solar Optical Telescope (SOT) aboard on the Hinode. As a result, it was found that the location of the two foot-points of the magnetic field lines well correspond to the flare ribbon. The result indicates that the NLFFF well capture the 3D structure of magnetic field in the flaring region. We further report the stability of the magnetic field by estimating the twist value of the field line and finally suggest the flare onset mechanism.The MHD virial theorem applied for observed photospheric field may be the one of way to estimate magnetic energy of generally invisible coronal magnetic structure. However, the photospheric field is not in a force-free state, so the application of virial theory needs some care. Here we use a series of MHD simulations of emerging field to investigate how we can apply the virial theorem to the emerging field. In early emerging phase, virial energy has a minus value although positive area at the photosphere is continuously generated toward a late emerging phase. We discuss why this tendency occurs. Then we derive the critical height where the actual emerging magnetic energy is almost comparable to the virial energy. If the difference between virial energy and magnetic energy becomes 10 percentage of the magnetic energy, we define this is the critical height, and assume the emerging field is close to force-free. We also discuss how the critical height changes with the initial twist of an emerging flux tube.We present the study of association between sub-photospheric flow and photospheric magnetic fields of active regions respectively derived from the local helioseismology and observed magnetic fields. It is believed that the energetic transients, e.g., flares and CMES, are caused by changes in magnetic and velocity field topologies in solar atmosphere. These changes are essentially brought about by the magnetic fields that are rooted beneath the photosphere where they interact and get affected by sub-photospheric flows. Therefore, we expect the topology of sub-surface flows to be correlated with the observable topology of magnetic fields at the photosphere and higher layers. In order to examine the correlation, if any, we computed the near photospheric flows and photospheric magnetic fields using the Doppler velocity and magnetic fields observations, respectively, provided by the SDO/HMI. The high resolution Doppler observations from the HMI enabled us to compute the very high p-modes parameters which sample the sub-photosphere shallow near the photosphere. Furthermore, we compute the sub-photospheric flow topology parameters, e.g., vorticity, kinetic helicity, and photospheric magnetic field topology parameters, e.g., magnetic helicity, from the magnetic fields observations to compare their associations. We present the result of the analysis in the paper.We use three-dimensional magnetohydrodynamic simulations to investigate how the dynamic state of emerging magnetic field is related to the twist of field lines. Emergence of magnetic field is considered as one of the key physical process producing solar activity such as flares, jets, and coronal mass ejections. To understand these activities we have to know dynamic nature and electric current structure provided by emerging magnetic field. To demonstrate dynamic nature of field lines, we focus on the factors such as curvature of magnetic field line and scale height of magnetic field strength. These factors show that strong twist case forms two-part structure in which the central part is close to a force-free state while the outer marginal part is in a fairly dynamic state. For weak twist case, it still shows two-part structure but the tendency becomes weaker than strong twist case. We discuss how the curvature distribution affects the dynamic nature of emerging magnetic field. We also investigate electric current distribution provided by emerging field lines to show a possible relation between electric current structure and sigmoid observed in a preflare phase.H${\alpha}$ transient bright kernels may be an important diagnostic of energy conversion processes occurring in the choromosphere during flares. We observed an H${\alpha}$ kernel that occurred in AR 11263 in associated with a small flare on 2011 Autust 5th using the Fast Imaging Solar Spectrograph installed at the 1.6m New Solar Telescope of Big Bear Solar Observatory. We find that both the H${\alpha}$ line and the CaII 8542${\AA}$ line appear in emission, with a red asymmetry in that they display red wings of enhanced emission. The red asymmetry shows 5-30 km/s downward motion for 8 minutes. We determine some physical parameters by adopting the Cloud mode and discuss the physical meaning of these results.We observed a surge associated with an Ellerman bomb using the Fast Imaging Solar Spectrograph(FISS) of the New Solar Telescope at Big Bear Solar Observatory. The surge was seen in absorption and varied rapidly both in H alpha and Ca II 8542 line. It originated from the Ellerman bomb, and was impulsively accelerated to 20km/s of the blueshift(upward) motion. Then the gradual change from blueshift of 20km/s to redshift of 40km/s occurred in 20 minutes. Based on the measured line-of-sight velocities, we estimated the material reached up to about 5,000km height. We inferred physical parameters of the surge by adopting the cloud model, and found that the temperature of the surge material was about 25,000K and the non-thermal velocity was about 10km/s. Our results suggest that the surge might be heated intensely after it was ejected from the Ellerman bomb.We investigate solar flare occurrence rate and daily flare probability depending on McIntosh sunspot classification, its area, and its area change. For this we use the NOAA active region and GOES solar flare data for 15 years (from January 1996 to December 2010). We consider the most flare-productive 10 sunspot classification: 'Dko', 'Dai', 'Eai', 'Fai', 'Dki', 'Dkc', 'Eki', 'Ekc', 'Fki', and 'Fkc'. Sunspot area and its change can be a proxy of magnetic flux and its emergence/cancellation, respectively. we classify each sunspot group into two sub-groups: 'Large' and 'Small'. In addition, for each group, we classify it into three sub-groups according to sunspot group area change: 'Decrease', 'Steady', and 'Increase'. As a result, in the case of compact groups, their flare occurrence rates and daily flare probabilities noticeably increase with sunspot group area. We also find that the flare occurrence rates and daily flare probabilities for the 'Increase' sub-groups are noticeably higher than those for the other sub-groups. In case of the (M+X)-class flares of 'Dkc' group, the flare occurrence rate of the 'Increase' sub-group is three times higher than that of the 'Steady' sub-group. Mean flare occurrence rates and flare probabilities for all sunspot regions increase with the following order: 'Steady', 'Decrease', and 'Increase'. Our results statistically demonstrate that magnetic flux and its emergence enhance major solar flare occurrence. We are going to forecast solar flares based on these results and NOAA scale.We have investigated a coronal jet observed near the limb on 2010 June 27 by the Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), and Solar Optical Telescope (SOT), and the SDO/Atmospheric Imaging Assembly (AIA), Helioseismic and Magnetic Imager (HMI), and on the disk by STEREO-A/EUVI. From EUV (AIA and EIS) and soft X-ray (XRT) images we have identified both cool and hot jets. There was a small loop eruption in Ca II images of the SOT before the jet eruption. Using high temporal and multi wavelength AIA images, we found that the hot jet preceded its associated cool jet by about 2 minutes. The cool jet showed helical-like structures during the rising period. According to the spectroscopic analysis, the jet's emission changed from blue to red shift with time, implying helical motions in the jet. The STEREO observation, which enabled us to observe the jet projected against the disk, showed that there was a dim loop associated with the jet. We have measured a propagation speed of ~800 km/s for the dimming front. This is comparable to the Alfven speed in the loop computed from a magnetic field extrapolation of the HMI photospheric field measured 5 days earlier and the loop densities obtained from EIS Fe XIV line ratios. We interpret the dimming as indicating the presence of Alfvenic waves initiated by reconnection in the upper chromosphere.Radiation Belt, discovered by Van Allen in 1958, is a region energetic particles are trapped by the Earth's magnetic field. To measure charged particles and fields in the radiation belt, RBSP(Radiation Belt Storm Probes) mission will be launched in September 2012 by NASA. RBSP mission consists of two spacecraft having orbit from 600 km to 30,000 km and rotates the Earth twice a day. This mission is not designed just for scientific purpose but have operational function broadcasting real time data for space weather monitoring. As a program of KASI-NASA cooperation, KASI is constructing RBSP data receiving antenna that will be installed by April in Daejeon. With this antenna system, NASA can receive RBSP data for 24 hours and KASI also get space weather information to protect Korean GEO satellites. In this presentation, we will discuss how we use RBSP data for space weather forecasting. In addition, we will talk about science topics that can be achieved by RBSP mission. Especially we focus on the dusk-side electron precipitation that has been considered as a main mechanism of electron dropout events. We show the dusk-side precipitation is closely associated with radiation belt electron loss with NOAA-POES data, and why RBSP mission is important to understand radiation belt physics.Understanding the dynamics of relativistic electron acceleration, loss, and transport in the Earth's radiation belt during magnetic storms is a challenging task. The U.S. National Science Foundation's Geospace Environment Modeling (GEM) has identified five magnetic storms for in-depth study that occurred during the second half of the Combined Release and Radiation Effects Satellite (CRRES) mission in the year 1991. In this study, we show the responses of relativistic radiation belt electrons to the magnetic storms by comparing the time-dependent 3-D Versatile Electron Radiation Belt (VERB) simulations with the CRRES MEA 1 MeV electron observations in order to investigate the relative roles of the competing effects of previously proposed scattering mechanisms at different storm phases, as well as to examine the extent to which the simulations can reproduce observations. The major scattering processes in our model are radial transport due to Ultra Low Frequency (ULF) electromagnetic fluctuations, pitch-angle and energy diffusion including mixed diffusion by whistler mode chorus waves outside the plasmasphere, and pitch-angle scattering by plasmaspheric hiss inside the plasmasphere. We provide a detailed description of simulations for each of the GEM storm events.Hwang, Jung-A;Lee, Dae-Young;Kim, Kyung-Chan;Choi, Eun-Jin;Shin, Dae-Kyu;Kim, Jin-Hee;Cho, Jung-Hee 90.2
Geosynchronous electron flux dropouts are most likely due to fast drift loss of the particles to the magnetopause (or equivalently, the "magnetopause shadowing effect"). A possible effect related to the drift loss is the radial diffusion of PSD due to gradient of PSD set by the drift loss effect at an outer L region. This possibly implies that the drift loss can affect the flux levels even inside the trapping boundary. We recently investigated the details of such diffusion process by solving the diffusion equation with a set of initial and boundary conditions set by the drift loss. Motivated by the simulation work, we have examined observationally the energy spectrum and pitch angle distribution near trapping boundary during the geosynchronous flux dropouts. For this work, we have first identified a list of geosynchronous flux dropout events for 2007-2010 from GOES satellite electron measurements and solar wind pressures observed by ACE satellite. We have then used the electron data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft measurements to investigate the particle fluxes. The five THEMIS spacecraft sufficiently cover the inner magnetospheric regions near the equatorial plane and thus provide us with data of much higher spatial resolution. In this paper, we report the results of our investigations on the energy spectrum and pitch angle distribution near trapping boundary during the geosynchronous flux dropout events and discuss implications on the effects of the drift loss on the flux levels at inner L regions.지구 자기권의 입자분포는 지구 자기권의 상태와 태양풍의 물리적 상황에 따라 다르다. 가령, 정지궤도에서 고에너지 입자의 flux가 낮아지는 것이 관측된다. 이러한 flux dropout 기간은 대부분 storm main phase에 해당된다. 반면 태양풍의 속력이 상대적으로 높은 HSS(high speed stream)기간 동안에는 대부분 정지궤도에서의 고에너지 입자 flux가 높아지며 radiation belt의 고에너지 입자들의 seed electron 역할을 할 것으로 예상하고 있다. 본 연구에서는 GOSE 11 위성의 electron flux data와 태양풍의 속도를 이용하여 HSS, quiet time, flux dropout 기간을 정의 하였다. 또한, 지구로부터 7~8Re 떨어진 night side지역을 radiation belt의 trapping boundary 바로 바깥 경계지역과 같다고 가정하였다. 그리고 각 기간 동안 이 경계지역에서 입자들의 분포와 관련된 물리적 조건을 결정하는 것을 목표로 하였다. 이는 방사선 벨트 내부에서의 역학적 진화에 영향을 미칠 수 있다. 2007년 6월부터 2010년 8월까지 이러한 경계지역에 THEMIS 위성이 위치했을 때 ESA와 SST의 omni-directional flux를 이용하여 에너지에 대한 입자플럭스 분포 함수를 산출하였다. 또한 각 기간에 평균한 분포 함수를 가장 잘 나타낼 수 있는 해석적 함수를 도출하였다. 추가로, 경계지역에서의 입자들의 pitch angle 분포 패턴도 결정 하였다. 이 결과는 방사선 벨트의 전산모사에서 실질적인 경계 조건으로 사용될 수 있다.Kokubun (1983) reported the local time variation of normalized amplitude of sudden commencement (SC) with a strong day-night asymmetry at geosynchronous orbit with 81 SC events. Further careful inspection of Kokubun's local time distribution reveals that the normalized SC amplitudes in the prenoon sector are larger than those in the postnoon sector. That is, there is a morning-afternoon asymmetry in the normalized SC amplitudes. Until now, however, there are no studies on this SC-associated morning-afternoon asymmetry at geosynchronous orbit. Motivated by this previous observation, we investigate a large data set (422 SC events in total) of geosynchronous SC observations and confirm that the geosynchronous SC amplitudes is larger in the morning sector than in the afternoon sector. This morning-asymmetry is probably caused by the enhancement of partial ring current, which is located in the premidnight sector, due to solar wind dynamic pressure increase. We also examine the latitudinal and seasonal variations of the normalized SC amplitude. We find that the SC-associated geosynchronous magnetic field perturbations are dependent on the magnetic latitude and season of the year. This may be due to the location of the magnetopause and cross-tail currents enhanced during SC interval with respect to geosynchronous spacecraft position.In this work we have examined the performance of the WSA/ENLIL cone model provided by Community Coordinated Modeling Center (CCMC). The WSA/ENLIL model simulates the propagation of coronal mass ejections (CMEs) from the Sun into the heliosphere. We estimate the shock arrival times at the Earth using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters from Michalek et al. (2007) as well as their associated interplanetary (IP) shocks. We make a comparison between CME arrival times by the WSA/ENLIL cone model and IP shock observations. For the WSA/ENLIL cone model, the root mean square(RMS) error is about 13 hours and the mean absolute error(MAE) is approximately 10.4 hours. We compared these estimates with those of the empirical model by Kim et al.(2007). For the empirical model, the RMS and MAE errors are about 10.2 hours and 8.7 hours, respectively. We are investigating several possibilities on relatively large errors of the WSA/ENLIL cone model, which may be caused by cone model velocities, CME density enhancement factor, or CME-CME interaction.Previous simulations posed a problem that they used reduced ion to electron mass ratios to save computation time. It was assumed that ion and electron dynamics are sufficiently separated, but it was not clearly verified. In this study, we examine the effect of ion to electron mass ratios on the generation of ion holes by ion beam driven instability. Ion holes are generated via electron holes in an applied electric field with the given initial condition. First, the ion acoustic instability is excited and nonlinearly develops. After the ion acoustic instability nonlinearly develops, the ion two-stream instability is excited and develops into ion holes. This implies that the previously suggested ion beam driven instability is strongly affected by the coupling between ions and electrons and the ion to electron mass ratio is important on the development of the instability. The energy transition and detail variation is different as reduced mass ratio under the same observation value based on FAST satellite. Although, the parameters are rescaled by conserving the kinetic energy to obtain the proper results, the nonlinear evolution is not perfectly identical.In this study, we investigated the generation of consecutive electrostatic solitary waves (ESWs) using by one-dimensional electrostatic particle-in-cell (PIC) simulation. For a given Gaussian perturbation, it is found that electron two-stream instability occurs in local grids region. Thus because of this instability, the electrostatic potential grows rapidly so as to be separated into electron and ion in perturbation region, and then electrons are trapped with heating during growing instability. It is found that these heated and trapped electrons are caused the generation of ESW, and ions are reflected backward and forward at the boundary of the initial perturbation, then form cold ion beam whereas electrons are confined to inside of the potential. Furthermore backward reflected ion beam forms ion holes by ion two-stream instability. On the other hand, as the confined electrons are released, and then released electrons also form hot electron beam, which play an important role in the generation of consecutive ESWs such as broadband electrostatic noise (BEN) observed frequently in space environment. Therefore the reason of the generation of consecutive ESWs is the existence of heated electrons which can sufficiently support energy to produce ESWs.Point Spread Function (PSF) is one of the most important optical characteristics for describing the performance of a telescope. And a concept of subpixelization is inevitable in evaluating the undersampled PSF (Shin and Sakurai 2009). Then, the internal structure of Yohkoh SXT CCD pixel is not uniform: For the top half of pixel area, the X-ray should pass a so-called gate structure where the charges are transferred to an output amplifier. This gate structure shows energy-dependent sensitivity (Tsuneta et al. 1991). For example, for Al-K (8.34 A) X-ray emission, the transmission of the polysilicon gate is about 0.9. Also, for the peak coronal response of the SXT thin filters, around 17 angstrom (0.729 keV), the transmission of the gate is about 0.6, falling off sharply towards longer wavelengths. It should be noted that this spectrally dependent non-uniform response of each CCD pixel will certainly have a noticeable effect on the properties of the PSF at longer wavelengths. Therefore, especially for analyzing the undersampled PSF of low energy source, a careful consideration of non-uniform internal pixel structure is required in determining the shape of the PSF core. The details on the effect of gate structure will be introduced in our presentation.천리안위성은 우리나라 최초의 정지궤도복합위성(COMS: Communication, Ocean, and Meteorological Satellite)으로 2010년 6월 27일, 남미 기아나 쿠루기지에서 아리안-5 로켓에 의해 발사된 후 동경 128.2도, 적도 상공 약 35,800 km 고도의 정지궤도에 안착되었다. 이 후 궤도상시험 기간과 안정화 기간을 거쳐 2011년 4월 1일, 기상청은 위성자료 서비스를 시작하였다. 천리안위성의 기상영상기는 한반도 주변의 기상변화와 전 지구적 기후 변화 및 대기 운동을 감시하기 위해 실시간 관측 및 전송 시스템을 갖춘 탑재체이다. 이 기상영상기는 하루 8번의 지구 반면 영역과 각각 80번 내외의 북반구 및 한반도 영역을 관측하며, 이 자료는 지상에서 복사보정과 기하보정을 거친 후 위성을 통해 다시 사용자에게 배포된다. 천리안위성 기상영상기는 쉼 없이 관측하고, 일정 시간 이내에 그 자료를 배포해야 한다. 이러한 자료서비스는 운영시스템의 장애나 자연현상에 의한 자료 미수신 혹은 미처리가 발생할 경우 운영 결과 및 성과에 영향을 미친다. 이와 같은 장애에 대비해 국가기상위성센터는 이중화된 시스템을 구축했으며, 자료 백업 부기관으로서 한국항공우주연구원과의 사이트 이중화도 시행하고 있다. 그러나 정지궤도에 있는 위성과 태양 및 지구의 역학적인 관계에 따라 태양 전파 잡음의 영향인 태양간섭과, 위성 태양전지판 충전 장애를 일으킬 수 있는 위성식, 그리고 위성 자정 주변에 발생할 수 있는 태양광 침입 및 산란광 영향 등은 미리 예측되어야 하며, 이 시기 운영 방안 마련과 사용자 공지 등의 조치가 수반되어야 한다. 국가기상위성센터는 춘 추분 시기에 발생하는 이러한 태양 영향을 예측하고 검증했으며, 이 시기 위성 및 지상국의 효율적인 운영방안을 마련하였다.흑점과 오로라의 역사적 기록은 단편적이고 관측 빈도에 의존하는 문제도 있지만 과거 태양활동의 실제 모습을 보여주는 중요한 자료이다. 또한 지구 대기에 유입된 cosmic ray에 의해 만들어지는 14C이나 10Be 그리고 18O와 같은 동위원소들이 나무 테나 polar ice 그리고 바다의 퇴적물 등에 축적되어 나타나는 Proxy data와 함께 과거 태양의 활동뿐만 아니라 지구의 자기장이나 기후 변화 등을 연구하는데 중요한 지표로 사용된다. 최근 태양의 활동과 지구 기후 변화의 관계에 대해 특별히 많은 관심이 집중되고 있으며 많은 연구가 진행되고 있다. 이 연구는 우리 역사서에 실린 흑점과 오로라의 역사적 기록 및 태양의 proxy data를 함께 비교하여 지난 1000년간 태양활동에서 나타난 특징들, 즉 흑점의 출현과 오로라 발생사이의 밀접한 관계 및 태양활동의 장단기 주기변화 그리고 Maunder Minimum과 같은 최대 극소기 때 보이는 기후 변화와 태양활동의 특징 등에 대해 논의해 보고자 한다.Halo coronal mass ejections (HCMEs) are major cause of geomagnetic storms and their three dimensional structures are important for space weather. In this study, we compare three cone models: an elliptical cone model, an ice-cream cone model, and an asymmetric cone model. These models allow us to determine the three dimensional parameters of HCMEs such as radial speed, angular width, and the angle (${\gamma}$ ) between sky plane and cone axis. We compare these parameters obtained from three models using 62 well-observed HCMEs from 2001 to 2002. Then we obtain the root mean square error (RMS error) between maximum measured projection speeds and their calculated projection speeds from the cone models. As a result, we find that the radial speeds obtained from the models are well correlated with one another (R > 0.84). The correlation coefficients between angular widths are less than 0.53 and those between${\gamma}$ values are less than 0.47, which are much smaller than expected. The reason may be due to different assumptions and methods. The RMS errors of the elliptical cone model, the ice-cream cone model, and the asymmetric cone model are 213 km/s, 254 km/s, and 267 km/s, respectively. Finally, we discuss their strengths and weaknesses in terms of space weather application.We have compared the geoeffective parameters of halo coronal mass ejections (CMEs) to predict geomagnetic storms. For this we consider 50 front-side full halo CMEs whose asymmetric cone model parameters and earthward direction parameter were available. For each CME we use its projected velocity (Vp), radial velocity (Vr), angle between cone axis and sky plane (${\gamma}$ ) from the cone model, earthward direction parameter (D), source longitude (L), and magnetic field orientation (M) of the CME source region. We make a simple and multiple linear regression analysis to find out the relationship between CME parameters and Dst index. Major results are as follows. (1)$Vr{\times}{\gamma}$ has a higher correlation coefficient (cc = 0.70) with the Dst index than the others. When we make a multiple regression of Dst and two parameters ($Vr{\times}{\gamma}$ , D), the correlation coefficient increases from 0.70 to 0.77. (2) Correlation coefficients between Dst index and$Vr{\times}{\gamma}$ have different values depending on M and L. (3) Super geomagnetic storms (Dst${\leq}$ -200 nT) only appear in the western and southward events. Our results demonstrate that not only the cone model parameters together with the earthward direction parameter improve the relationship between CME parameters and Dst index but also the source longitude and its magnetic field orientation play a significant role in predicting geomagnetic storms.Various electromagnetic fluctuations are observed in the upstream of Earth's bow shock. Properties of plasmas are important in determining the development of the fluctuations. In this study we analyze the phase space distribution functions of plasmas measured by the Cluster spacecraft to understand how the fluctuations develop. Plasmas in the upstream of Earth's bow shock often consist of multiple components, especially when the fluctuations exist. In addition to the solar wind beams, backstreaming ion beams and diffuse ions are also often observed separately or simultaneously. The solar wind beams are not much perturbed even within the fluctuations. The diffuse ions are more than 10 times hotter than the solar wind beams and the backstreaming beams intermediate between them. The distribution functions of the diffuse and backstreaming ions are anisotropic to the magnetic field. Thus, they may be responsible for the fluctuations associated with temperature anisotropy. We will discuss about the thermalization processes and the relationship between the fluctuations and plasmas.We statistically examined ULF Pc 3-5 wave power in the regions of undisturbed upstream solar wind, quasi-parallel shock (and foreshock), quasi-perpendicular shock, and the magnetosheath to understand how and to what extent the wave power changes as the solar wind propagates to the magnetosheath. For this study, we used the magnetic field data from the THEMIS spacecraft and Wind (as shifted to the bow shock nose) for May-November in 2008 and 2009. The statistical results show that, in the case of the Pc5 wave power, the sheath power is roughly proportional to the upstream power for both quasi-parallel (and foreshock) and quasi-perpendicular shock regions. Also we identified undisturbed upstream condition from WIND as being well away from foreshock region, and found that the sheath power can be larger for quasi-parallel shock region by a factor of 5-15 than for quasi-perpendicular shock region. In the cases of Pc 3 and Pc4 waves, we found the higher sheath power when associated with the foreshock than with the quasi-perpendicular shock region.The Hayabusa mission successfully rendezvoused with its target asteroid 25143 Itokawa in 2005 and brought the asteroidal sample to the Earth in 2009. This mission enabled to connect the S-type asteroids to ordinary chondrites, the counterpart meteorites which exist in near Earth orbit. Recent finding of a fragment from 25143 Itokawa [1] suggested that the asteroid experienced an impact after the injection to the near-Earth orbit. In this presentation, we investigated the evidence of the recent impact on 25143 Itokawa using the onboard camera, AMICA. AMICA took more than 1400 images of Itokawa during the rendezvous phase. It is reported that AMICA images are highly contaminated by lights scattered inside the optics in the longer wavelength. We developed a technique to subtract the scattered light by determining the point spread functions for all available channels. As the result, we first succeeded in the determination of the surface spectra in all available bands. We consider a most fresh-looking compact crater, Kamoi, is a possible impact site.It has been speculated that there could be dormant or extinct comets in the list of known asteroids, which appear asteroidal but are icy bodies originating from outer solar system. However, little is known about the existence of such objects not only because of their complicated chaotic orbits but also because of the limited physical and chemical information. AKARI infrared space mission gave us brand-new albedo catalog of Near Earth Objects, which clues in a better understanding of dark asteroids using both albedo data and dynamical models could be possible. Dark Asteroids with low () albedos are thought to be dormant or extinct comet candidates due to its similar albedo values with comet nucleus. In addition to this, dynamical models indicate that candidate cometary objects have Tisserand parameter. Based on both observational and dynamical criteria, we obtained 196 dark asteroids lists. We numerically integrated backward their orbits using the N-body code Mercury6 (Chambers 1999) during 10 million years to track the past orbits of bodies. We picked out 14 comet candidates that show abnormal orbits in the past by analyzing orbital elements among 196 candidates. From the dynamical evolution simulations, we finally obtained 3 most-likely comet candidates; 944Hidalgo,2006QL39,andP/SidingSpring.Twoofthemareconsistent with past research; P/Siding Spring is a known comet and 944 Hidalgo is a most-likely comet candidate in asteroid populations. Since they all have stable orbits in nowadays although they have unstable orbit in the past, we could conclude that they may be not active comets but dormant or extinct comets.Hapke의 양방향 분포 함수를 균일하게 입힌 실 크기 3차원 달표면 BRDF 모델을 이용한 달의 조도 수치모사 와 Big Bear Solar Observatory(BBSO)의 달빛 조도 관측 결과를 비교하였다. 1999년 9월 5일 UT9:30에서 UT12:30까지 지구상의$34^{\circ}$ 15'30.04"N$116^{\circ}$ 55'16.49"W 위치에서 계산된 달의 조도가 관측된 조도와 1% 이내의 차이를 보이는 것을 확인하였다. 이후 검증된 달의 BRDF 모델과 램버시안 산란 지구 모델을 이용해 시간별 전 지구 알베도 추이를 광선 추적 수치 모사한 결과와 실제 BBSO에서의 측정결과 간 1% 이내의 차이를 보이는 것을 확인하여, .BRDF 모델과 광선추적 수치모사 기법의 타당성을 검증하였다.혜성에서 방출되는 CH 분자는 핵에서 방출되어 태양 빛에 의해 분해되는 시간인 lifetime이 짧다. Lifetime이 짧은 분자는 모든 energy state로의 천이가 충분히 일어나 안정된 상태인 fluorescent equilibrium상태에 도달하기 전에 분해되어 버리기 때문에 혜성 속의CH의 특성을 파악하기 위해서는 Time-dependent calculation이 꼭 필요하다. Time-dependent calculation 은 CH 분자가 핵에서 방출된 후 시간에 따라 변하는population을 계산함으로써 각 혜성의 조건에 알맞은 CH model을 얻을 수 있어 혜성에서 방출되는 분자들을 연구하기에 적합한 방법이다. 우리는 BOES로 관측한 Machholz(C/2004 Q2), 103P/Hartley혜성을 포함한 Hyakutake (C/1996 B2)혜성과 Austin (1990V)혜성의 고분산 분광자료를 이용하여 Time-dependent calculation 을 실시하였고, 그 결과를 소개하고자 한다.Lunar limb profiles are needed for analyses of lunar occultations and solar eclipses. The lunar limb profile data by C.B. Watts (1963) have been used for such analyses, but it has been found that there are many kinds of errors in the data by Watts, which seriously affected the results obtained from the analyses of the observations. Recently very precise lunar topographic data were obtained by the Japanese lunar explorer Kaguya and NASA's Lunar Reconnaissance Orbiter. I obtained lunar limb profiles for any lunar librations from them. I will show how well the lunar limb profiles fit to observed ones from lunar grazing occultations. By combining the accurate lunar limb profiles with observations of lunar occultations we can detect errors in the Hipparcos stellar reference frame. By analyzing Baily's beads timing observations of past total and annular solar eclipses using the accurate lunar limb profiles we will be able to detect solar diameter variations.We have investigated excitation processes of the 3-micron bands of$CH_4$ ,$C_2H_2$ , and$C_2H_6$ over the auroral regions of Jupiter including particle bombardments, Joule heating, scattering of solar radiation, and possible chemiluminescence. We also considered possible LTE or Non-LTE conditions of these processes. We constructed particle precipitation models including$H_2$ , He, H, and the hydrocarbon molecules for the atmosphere of the auroral regions. We present preliminary results from these models, and comparisons of the model results with spectroscopic observations in the 3 micron wavelength range of Jupiter.Interplanetary dust particles are observable as zodiacal light, which is the sunlight scattered by the interplanetary dust particles. The origins of interplanetary dust particles are still in question because they are eroded by Poynting-Robertson photon drag and mutual collisions among dust particles. The small-scale structures in the zodiacal light provided a clue to specify their origins. Asteroidal debris were detected as band-like structures (dust bands), and the cometary large particles were detected as narrow trails (dust trails). However, little is confirmative about their detailed origins and mineralogical compositions because of the lack of observational data particularly in the optical wavelength. We made a high-resolution optical zodiacal light map based on the CCD observations at Mauna Kea, Hawaii. We analyzed data taken on November 12, 2004. After the data reduction, such as flat fielding and subtraction of airglow emissions, we succeeded in the construction of the zodiacal light map with the spatial resolution of 3' in the solar elongation between 45 degree and 180 degree. This is the highest resolution map in the visible wavelength so far. In this map, we confirmed the dust bands structures near the ecliptic plane. We will discuss about the similarities and the differences between optical and infrared dust bands.An asteroid family is a population of asteroids in the proper orbital element space (a, e, i), considered to have been produced by a disruption of a large parent body presumably through a catastrophic collision. Asteroid families offer unique opportunities to reconstruct and characterize the break-up history of airless bodies in the main-belt. The Maria family is a typical old population (~3${\pm}$ 1 Gyr) of asteroids that have undergone significant collisional and dynamical evolution in the history of the inner Solar System; it is also believed to be one of the candidate source regions for giant S-type near-earth asteroids (NEAs). However, to date, physical characteristics of this family members such as rotational periods have been known only for 61 of the larger asteroids among 3,230 objects, which accounts for less than 2 percent of the family. In this presentation, we provide some preliminary results of our recent study: out of more than dozen of the family members, lightcurves for eight objects have been obtained for the first time. We plan to increase the number of target objects, and investigate evidences for the Yarkovsky/YORP effect on Maria family based on our observations.
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