• 천문학회지
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• 제41권6호
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• pp.157-161
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• 2008

We have estimated the fractal dimension of the molecular clouds associated with the Hii region Sh 156 in the Outer Galaxy. We selected the $^{12}CO$ cube data from the FCRAO CO Survey of the Outer Galaxy. Using a developed code within IRAF, we identified slice-clouds (2-dimensional clouds in velocity-channel maps) with two threshold temperatures to estimate the fractal dimension. With the threshold temperatures of 1.8 K, and 3 K, we identified 317 slice-clouds and 217 slice-clouds, respectively. There seems to be a turn-over location in fractional dimension slope around NP (area; number of pixel) = 40. The fractal dimensions was estimated to be D = $1.5\;{\sim}\;1.53$ for $NP\;{\geq}\;40$, where $P\;{\propto}\;A^{D/2}$ (P is perimeter and A is area), which is slightly larger than other results. The sampling rate (spatial resolution) of observed data must be an important parameter when estimating fractal dimension. Fractal dimension is apparently invariant when varying the threshold temperatures applied to slice-clouds identification.

• 천문학회지
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• 제38권2호
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• pp.215-218
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• 2005

An atlas of high resolution (${\lambda}/{\Delta}{\lambda}$=45,000) profiles of interstellar atomic lines of K I (7665, 7699 ${\AA}$), Na I (D 1, D2), Ca II (H, K), Ca I (4227 ${\AA}$), molecular structures of CH, CH+, CN and the major diffuse interstellar bands at 5780 and 5797 ${\AA}$ based on ${\~}$300 echelle spectra of ${\~}$200 OB stars is presented. Relationships between the reddenings, distances and equivalent widths of NaI, CaII, KI, CH, CH+, CN and diffuse bands are discussed. The equivalent width of K I (7699 ${\AA}$) as well as of CH4300 ${\AA}$ / correlate very tightly with E(B- V) in contrast to the features of neutral sodium, ionized calcium and the molecular ion CH+. The equivalent widths of the Hand K lines of Call grow with distance at a rate ${\~}$250m${\AA}$ per 1 kpc. A similar relation for NaI is much less tight. The strengths of neutral potassium lines, molecular features and diffuse interstellar bands do not correlate practically with distance. These facts suggest that ionized calcium fills the interstellar space quite homogeneously while the other carriers mentioned above, especially K I, CH and these of diffuse bands occupy more and more compact volumes, also filled with dust grains. Apparently the carriers of narrow diffuse bands are spatially correlated with simple molecules and dust grains - all abundant in the so-called 'zeta' type clouds. The same environment seems to be hostile to the carriers of broad diffuse interstellar bands (DIEs) (like 5780 or 6284) and -to a certain extent - also to CaII, NaI and CH+.

• 천문학논총
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• 제32권1호
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• pp.105-107
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• 2017

We present results of AKARI/IRC near-infrared (NIR) slit-spectroscopy ($2.5-5.0{\mu}m$, R ~ 100) of Galactic sources, focusing on ice absorption features. We investigate the abundance of $H_2O$ and $CO_2$ ices and other ice species (CO and XCN ices) along lines of sight towards Galactic H $\small{II}$ regions, massive YSOs, and infrared diffuse sources. Even among those different kinds of astronomical objects, the abundance ratio of $CO_2$ to $H_2O$ ices does not vary significantly, suggesting that the pathway to $CO_2$ ice formation driven by UV irradiation is not effective at least among the present targets.

• 한국항행학회논문지
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• 제11권1호
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• pp.64-71
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• 2007

본 논문에서는 ISM(Industrial, Scientific, Medical)대역과 Wireless LAN대역을 위한 S-band에서 동작하는 마이크로스트립 안테나를 설계 및 제작을 하였다. 기존의 사각패치 안테나 소자가 아닌 원형패치 안테나 소자 4개를 평면상에 $2{\times}2$로 배열하였다. 단일 원형패치의 크기를 계산하여 최적화하였으며 방사소자 간의 간격을 $0.24{\lambda}$로 배열하였다. 원형패치 안테나 소자를 사용함으로써 기존의 사각패치 안테나 소자를 이용한 것 보다 8%의 크기를 감소시켰다. 제안된 안테나는 E-평면에서는 안테나 이득 12.7 [dBi], 3 dB 빔폭은 $40^{\circ}$를 나타냈으며 H-평면에서는 안테나 이득 12.1 [dBi], 3 dB 빔폭은 $45^{\circ}$라는 특성을 나타내었으며, 250[MHz]의 대역폭 (VSWR < 2)을 얻었다.

• 천문학논총
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• 제30권2호
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• pp.75-78
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• 2015

A growing body of evidence has been supporting the existence of so-called "dark molecular gas" (DMG), which is invisible in the most common tracer of molecular gas, i.e., CO rotational emission. DMG is believed to be the main gas component of the intermediate extinction region from Av~0.05-2, roughly corresponding to the self-shielding threshold of $H_2$ and $^{13}CO$. To quantify DMG relative to $H{\small{I}}$ and CO, we are pursuing three observational techniques; $H{\small{I}}$ self-absorption, OH absorption, and THz $C^+$ emission. In this paper, we focus on preliminary results from a CO and OH absorption survey of DMG candidates. Our analysis shows that the OH excitation temperature is close to that of the Galactic continuum background and that OH is a good DMG tracer co-existing with molecular hydrogen in regions without CO. Through systematic "absorption mapping" by the Square Kilometer Array (SKA) and ALMA, we will have unprecedented, comprehensive knowledge of the ISM components including DMG in terms of their temperature and density, which will impact our understanding of galaxy evolution and star formation profoundly.

• 천문학회보
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• 제40권2호
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• pp.31.3-32
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• 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.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.580-583
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• 2007

본 논문에서는 슬롯 안테나 구조를 변형하여 ISM용 마이크로스트립 슬롯 안테나를 제안했다. 제안된 안테나는 기존의 슬롯 안테나 급전 구조에 변형된 급전선로를 이용하여 이중대역에서 공진주파수가 나타나도록 설계 제작하였다. 설계된 안테나는 2.45 GHz, 5 GHz의 중심 주파수에서 각각 8.23%, 4.8%의 대역폭을 갖고, 변형된 급전선로의 길이변화에 따라 대역폭과 공진주파수가 변화하였다. 또한, 제작된 안테나의 방사 패턴 특성은 각각 주파수에서 E면과 H면의 특성이 비교적 양호하게 측정되었다.

• 한국인터넷방송통신학회논문지
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• 제22권4호
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• pp.35-40
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• 2022

본 논문은 전자제품의 PCB 기판 외곽에 위치시켜 ISM 대역에서 무선통신이 가능하도록 하는 안테나를 제안하였다. PCB에서는 부품의 간섭 또는 디자인에 방해가 되지 않도록 소형화하기 위해 T자형 OPEN - STUB 급전선을 설계하였다. T자형 스터브 급전선과 스파이럴 구조를 이용하여 각각 2.4GHz, 5.8GHz 대역에서 안테나의 특성을 확인하였다. 실험을 위하여 안테나 크기는 가로 5mm × 세로 6.5mm의 크기로 하였으며 PCB두께는 1.2T로 하여 제작하였다. 제작된 안테나의 실험 측정결과 2.4GHz, 5.8GHz에서 -10dB 이상의 반사손실을 얻을 수 있었다. 또한 E-plane에서 이득은 -4.45dBi로 나타났으며, H-plane에서 이득은 -1.05dBi 나타났다. 따라서 여기서 제안된 무선통신용 소형안테나에서 우수한 성능을 나타내었다.

• 천문학회지
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• 제37권4호
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• pp.281-284
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• 2004

Optical imaging and spectroscopy of G353.2+0.9, the brightest part of the giant H II region NGC 6357, shows that this H II region is optically thin, contains ${\~}300\;M_{\bigodot}$ of ionized gas and is probably expanding into the surrounding medium. Its chemical composition is similar to that found in other H II regions at similar galactocentric distances if temperature fluctuations are significant. The inner regions are probably made of thin shells and filaments, whereas extended slabs of material, maybe shells seen edge-on, are found in the periphery. The radio continuum and H$\alpha$ emission maps are very similar, indicating that most of the optical nebula is not embedded in the denser regions traced by molecular gas and the presence of IR sources. About $10^{50}$ UV photons per second are required to produce the H$\beta$ flux from the 1l.3'${\times}$10' region surrounding the Pis 24 cluster that is south of G353.2+0.9. Most of the energy powering this region is produced by the 03-7 stars in Pis 24. Most of the 2MASS sources in the field with large infrared excesses are within G353.2+0.9, indicating that the most recent star forming process occured within it. The formation of Pis 24 preceded and caused the formation of this new generation of stars and may be responsible for the present-day morphology of the entire NGC 6357 region.

• 천문학회지
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• 제37권4호
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• pp.285-288
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• 2004

Near-infrared imaging photometry supplemented by optical spectroscopy and narrow-band imaging of the H II region Sh 2-128 and its environment are presented. This region contains a developed H II region and the neighboring compact H II region S 128N associated with a pair of water maser sources. Midway between these, the core of a CO cloud is located. The principal ionizing source of Sh 2-128 is an 07 star close to its center. A new spectroscopic distance of 9.4 kpc is derived, very similar to the kinematic distance to the nebula. This implies a galactocentric distance of 13.5 kpc and z = 550 pc. The region is optically thin with abundances close to those predicted by galactocentric gradients. The $JHK_s$ images show that S 128N contains several infrared point sources and nebular emission knots with large near-infrared excesses. One of the three red Ks knots coincides with the compact H II region. A few of the infrared-excess objects are close to known mid- and far-infrared emission peaks. Star counts in J and $K_s$ show the presence of a small cluster of B-type stars, mainly associated with S 128N. The $JHK_s$ photometric properties together with the characteristics of the other objects in the vicinity suggest that Sh 2-128 and S 128N constitute a single complex formed from the same molecular cloud, with ages ${\~}10^6$ and < $3 {\times} 10^5$ years respectively. No molecular hydrogen emission was detected at 2.12 ${\mu}m$. The origin of this remote star forming region is an open problem.