• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.31.3-32
• /
• 2015

We present the physical properties of star forming regions in IC 10 obtained from Korea VLBI Network (KVN) 22GHz, the Submillimeter Array (SMA) CO, Very Large Array (VLA) HI 21cm, optical (U, B, V and H-alpha), and Spitzer infrared observations. IC 10 is a nearby (~0.7Mpc) irregular blue compact dwarf (BCD) galaxy which is likely to be experiencing an intense and recent burst of star formation. This nearby infant system showing high star formation rate but low metallicity (<20% of that of the Sun) provides critical environment of interstellar medium (ISM) under which current galactic star formation models are challenged. To make quantitative analysis of the ISM in the galaxy, we apply 2D cross-correlation technique to the multi-wavelength data for the first time. By cross-correlating different tracers of star formation, dust and gas phases in IC 10 in a two dimensional way, we discuss the gas properties and star formation history of the galaxy.

• Bulletin of the Korean Space Science Society
• /
• 2003.10a
• /
• pp.85-85
• /
• 2003

We examined the hypothesis that the crater formation rate exhibits periodicity, employing data sets of Grieve (1991), Moon et al. (2001), and the Earth Impact Database (2002; DB02). DB02 is known to supercede previous compilations in terms of its accuracy and precision of the ages; it is the first time that this database has been used for periodicity analysis. For data sets comprising impact structures with D$\geq$5km (and also those with $\geq$20km), there is no convincing evidence for periodicities in the crater ages, according to our Fourier analysis. However, we detected two peaks at 16.1Myr and 34.7Myr for craters with D$\geq$30km; we confirm that the age distribution of impact craters with D$\geq$45km has dominant power at 16.1Myr. Thus, we may conjecture a probable periodic shower of Earth impactors with sizes d$\geq$1.5km. In addition, we found that the selection of data sets, the lower limits on the ages and diameters of impact craters, as well as the accuracy and precision of the ages, all constitute crucial factors in reconstructing the impact cratering history of the Earth.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.39.1-39.1
• /
• 2015

Korea has a long history in astronomy, which is proved by many observational records written in Korean chronicles. There are 43 sunspot records in Goryeo dynasty (高麗 918-1392) and 13 records in Joseon dynasty (朝鮮 1392-1910). According to analysis of Korean historical records, it is known that sunspot records in Goryeo dynasty show well in match with the well-known solar activity of 11.3 years. It means that Korean historical sunspot records show real solar phenomena. Korean sunspot records also show that solar activity decrease in Joseon dynasty compared with the previous ~500 years. In order to know the change of solar activity in detail, we examine Korean historical atmospheric records which can indicate climate change. We first analyze historical frost records. Korean chronicles have around 600 frost records during the last millennium. We find that the climate change shows sign of cooling down when check the variation of epoch that the first and last frost events in each year are written. This result is well in accord with that of historical sunspot records. Therefore, we claim that solar activity decrease during the last thousand years.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.106.2-106.2
• /
• 2012

A Jupiter-family comet, 17P/Holmes, underwent an outburst on 2007 October 23. Since there has been no more dramatic comet outburst than the 17P/Holmes event in the history of modern astronomical observations, active observations were made soon after the outburst. However, little is known about the activity before the outburst because of the accidental event. In addition, since the nucleus has been veiled by the thick dust cloud by the 2007 outburst, the physical status of the nucleus was unknown. In this presentation, we investigated the contrast between before and after the outburst through the imaging observations in both optical and mid-infrared wavelengths. We thus analyzed data taken by Akari infrared telescope, Subaru 8-m telescope, University of Hawaii 2.2-m telescope and Nishi-Harima Astronomical Observatory 2-m Nayuta telescope. As the result, we found that the nucleus was significantly activated through the outburst. The surface fractional active area was 0.3% in the pre-outburst data while 10% in the past-outburst data. We expect that 17P/Holmes shows strenuous activity in the next return in 2013-2014.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.61.3-62
• /
• 2016

An asteroid family is a group of asteroidal objects in the proper orbital element space (a, e, and i), considered to have been produced by a disruption of a large parent body through a catastrophic collision. Family members usually have similar surface properties such as spectral taxonomy types, colors, and visible geometric albedo with a same dynamical age. Therefore an asteroid family could be called as a natural Solar System laboratory and is also regarded as a powerful tool to investigate space weathering and non-gravitational phenomena such as the Yarkovsky/YORP effects. We carry out time series photometric observations for a number of asteroid families to obtain their physical properties, including sizes, shapes, rotational periods, spin axes, colors, and H-G parameters based on nearly round-the-clock observations, using several 0.5-2 meter class telescopes in the Northern hemisphere, including BOAO 1.8 m, LOAO 1.0 m, SOAO 0.6 m facilities in KASI, McDonald Observatory 2.1 m instrument, NARIT 2.4 m and TUG 1.0 m telescopes. This study is expected to find, for the first time, some important clues on the collisional history in our Solar System and the mechanisms where the family members are being transported from the resonance regions in the Main-belt to the near Earth space.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.1
• /
• pp.36.2-36.2
• /
• 2013

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. The focal plane instruments onboard SPICA will enable us to resolve many astronomical key issues from the formation and evolution of galaxies to the planetary formation. The FPC-S (Focal Plane Camera - Sciecne) is a near-infrared instrument proposed by Korea as an international collaboration. Owing to the capability of both low-resolution imaging spectroscopy and wide-band imaging with a field of view of $5^{\prime}{\times}5^{\prime}$, it has large throughput as well as high sensitivity for diffuse light compared with JWST. In order to strengthen advantages of the FPC-S, we propose the studies of probing population III stars by the measurement of cosmic near-infrared background radiation and the star formation history at high redshift by the discoveries of active star-forming galaxies. In addition to the major scientific targets, to survey large area opens a new parameter space to investigate the deep Universe. The good survey capability in the parallel imaging mode allows us to study the rare, bright objects such as quasars, bright star-forming galaxies in the early Universe as a way to understand the formation of the first objects in the Universe, and ultra-cool brown dwarfs. Observations in the warm mission will give us a unique chance to detect high-z supernovae, ices in young stellar objects (YSOs) even with low mass, the $3.3{\mu}$ feature of shocked circumstance in supernova remnants. Here, we report the current status of SPICA/FPC project and its extragalactic sciences.

• Publications of The Korean Astronomical Society
• /
• v.27 no.4
• /
• pp.223-224
• /
• 2012

Understanding the birth and evolution of galaxies, and the history of star formation in them, is one of the most important problems in astronomy. Using the data from the AKARI IRC survey of the Large Magellanic Cloud at 3.2, 7, 11, 15, and $24{\mu}m$, we have constructed a multi-wavelength catalog containing data from the cross-correlation with a number of other databases at different wavelengths. We present the first approach with a Support Vector Machine (SVM)-based method to separate different classes of stars in LMC in the color-color and color-magnitude diagrams.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.50.4-51
• /
• 2015

Current and planned deep multicolor wide-area cosmological surveys will map in detail the spatial distribution of galaxies and quasars over unprecedented volumes, and provide a number of objects with photometric redshifts more than an order of magnitude bigger than that of spectroscopic redshifts. Photometric information is statistically more significant for studying cosmological evolution, dark energy, and the expansion history of the universe at a fraction of the cost of a full spectroscopic survey, but intrinsically carries a bias due to noise in the distance estimates. We provide convolution- and deconvolution-based algorithms capable of removing this bias -- thus able to exploit the full cosmological information -- in order to reconstruct intrinsic distributions and correlations between distance-dependent quantities. We then show some direct applications of our techniques to the VIMOS Public Extragalactic Redshift Survey (VIPERS) and the Sloan Digital Sky Survey (SDSS) datasets. Our methods impact a broader range of studies, when at least one distance-dependent quantity is involved; hence, they will be useful for upcoming large-volume surveys, some of which will only have photometric information.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.1
• /
• pp.32.1-32.1
• /
• 2013

We use numerical simulations to investigate the evolution of both the star formation rate (SFR) and the observable properties of equal-mass disk merger remnants for 18 different orbital configurations. In our analysis, the photometric properties of the remnants have been constructed by considering dust reddening effect in order to facilitate the comparison with observational data of large surveys such as the Sloan Digital Sky Survey (SDSS). First, we found that the detailed evolutions of merging galaxies are different between the merging characteristics such as merging time scale, SFR history, and burst efficiency. Around $70{\pm}5$ percent of gas turns into stars until the merger-induced starburst ends regardless of merger types. Our study also suggests that merger features involve a small fraction of stars. Merger features last roughly 3 times the final coalescence time of galaxy mergers. For a shallower surface brightness limit, the features seem to survive in a shorter time, which is the reason why detecting merger features by using shallow surveys were difficult in the past.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.2
• /
• pp.50.1-50.1
• /
• 2019

Ultra Metal-Poor (UMP; [Fe/H] < -4.0) stars are thought to be true second generation of stars. Thus, the chemistry and kinematics of these stars serve as powerful tools to understand the early evolution of the Milky Way (MW). However, only about 40 of these stars have been discovered thus far. To increase the number of these stars, we selected UMP candidates from low-resolution spectra (R ~ 2000) of the Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), and performed high-resolution (R ~ 40,000) spectroscopic follow-ups with Gemini/GARACES. In this study, we present chemical and kinematic properties of the observed UMP candidates, and infer the nature of their progenitors to trace the chemical enrichment history of the MW.