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1968년 ~ 2024년까지 1,211 건의 한국천문학회지를 격월간 확인하실 수 있습니다.
- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,211건 (DB Construction : 1,211 Articles)
총 게시글 1,211건
페이지 48/122
471
- OTA KAZUAKI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.179-182
- 2005
- 원문 바로보기
We conducted an extremely wide field survey of z <TEX>${\~}$</TEX> 6 Lyman break galaxies (LBGs) to precisely derive their bright end surface density overcoming the bias due to cosmic variance. We selected out LBG candidates in the Subaru/ XMM-Newton Deep Survey Field (SXDS) over the total of <TEX>${\~}1.0\;deg^2$</TEX> sky area down to <TEX>$z_{AB} = 26.0 ({\ge}3{\sigma},\;2'.0 aperture)$</TEX> using i' - z' > 1.5 color cut. This sample alone is likely to be contaminated by M/L/T dwarfs, low-z elliptical galaxies, and z <TEX>${\~}$</TEX> 6 quasars. To eliminate these interlopers, we estimated their numbers using an exponential disk star count model, catalogs of old ellipticals in the SXDS and other field, and a z<TEX>${\~}$</TEX>6 quasar luminosity function. The finally derived surface density of z <TEX>${\~}$</TEX> 6 LBGs was 165 <TEX>$mag^{-1}\;deg^{-2}$</TEX> down to <TEX>$z_{AB}$</TEX> = 26.0 and shows good agreement with previous results from the narrower field survey of HST GOODS.
472
- SAKAI TAKESHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.257-260
- 2005
- 원문 바로보기
We have mapped the W 3 giant molecular cloud in the <TEX>$C^o\;^3P_1-^3 P_o$</TEX> ([CI]) line with the Mount Fuji Submillimeter-wave Telescope. The [CI] emission is extended over the molecular cloud, having peaks at three star forming clouds; W 3(Main), W 3(OH), and AFGL 333. The [CI] emission is found to be strong in the AFGL 333 cloud. We have also observed the <TEX>$C^{18}O,\;CCS,\;N_2H^+$</TEX>, and <TEX>$H^{13}CO^+$</TEX> lines by using the Nobeyama Radio Observatory 45 m telescope. In the AFGL 333 cloud, we find two massive cores, which are highly gravitationally bound and have no sign of active star formation. The high [<TEX>$C^o$</TEX>]/[CO] and [CCS]/[<TEX>$N_2H^+$</TEX>] abundance ratios suggest that the AFGL 333 cloud is younger than the W 3(Main) and W 3(OH) clouds.
473
- NAKAJIMA YASUSHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.173-174
- 2005
- 원문 바로보기
On behalf of the IRSF/SIRIUS group, I introduce some recent results from our deep near-infrared surveys (J, Hand Ks bands, limiting magnitude of Ks=17) toward star forming regions in the Milky Way Galaxy (MWG) and Large Magellanic Cloud (LMC) with the near-infrared camera SIRIUS. We discovered a rich population of low-mass young stellar objects associated with the W3 and NGC 7538 regions in the MWG based on the near-infrared colors arid magnitudes. The high sensitivity of our survey enables us to detect intermediate-mass pre-main sequence stars, i.e. HAEBE stars, even in the LMC. We detected many HAEBE candidate stars in the N159/N160 complex star forming region in the LMC with the IRSF 1.4-m telescope. Spatial distributions of the young stellar objects indicate the sequential cluster formation in each star forming region in the complex and large scale (a few <TEX>${\times}$</TEX> 100 pc) sequential cluster formation over the entire complex.
474
- ICHIMOTO KIYOSHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.307-310
- 2005
- 원문 바로보기
The Solar-B is the third Japanese spacecraft dedicated for solar physics to be launched in summer of 2006. The spacecraft carries a coordinated set of optical, EUV and X-ray instruments that will allow a systematic study of the interaction between the Sun's magnetic field and its high temperature, ionized atmosphere. The Solar Optical Telescope (SOT) consists of a 50cm aperture diffraction limited Gregorian telescope and a focal plane package, and provides quantitative measurements of full vector magnetic fields at the photosphere with spatial resolution of 0.2-0.3 arcsec in a condition free from terrestrial atmospheric seeing. The X-ray telescope (XRT) images the high temperature (0.5 to 10 MK) corona with improved spatial resolution of approximately 1 arcsec. The Extreme Ultraviolet Imaging Spectrometer (EIS) aims to determine velocity fields and other plasma parameters in the corona and the transition region. The Solar-B telescopes, as a whole, will enable us to explore the origins of the outer solar atmosphere, the corona, and the coupling between the fine magnetic structure at the photosphere and the dynamic processes occurring in the corona. The mission instruments (SOT/EIS/XRT) are joint effort of Japan (JAXA/NAO), the United States (NASA), and the United Kingdom (PPARC). An overview of the spacecraft and its mission instruments are presented.
475
- OHASHI NAGAYOSHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.103-106
- 2005
- 원문 바로보기
The Submillimeter Array (SMA), a collaborative project of the Smithsonian Astrophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy & Astrophysics (ASIAA), has begun operation on Mauna Kea in Hawaii. A total of eight 6-m radio telescopes comprise the array with currently working receiver bands at 230, 345, and 690 GHz. The array will have 8 receiver bands covering the frequency range of 180-900 GHz. The backend is flexible analog-digital correlator with a full bandwidth of 2GHz, which is very powerful to cover several line emissions simultaneously. The current status and future plans of the SMA are described with emphasis on Taiwanese efforts.
476
- ANN HONG BAE
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.121-124
- 2005
- 원문 바로보기
High resolution images of the nuclear regions of nearby galaxies show that nuclear spirals are preponderant in normal galaxies as well as in active galaxies. These nuclear spirals, especially the grand-design nuclear spirals are found to be formed by the gas flow driven by the bar. Hydrodynamical simulations exploring a wide range of parameter space show that the morphology of nuclear spirals depends not only on the inner dynamics but on the global dynamics resulting from the global mass distribution of galaxies. Thus, the nuclear morphology can be a diagnostic tool for the inner dynamics of galaxies when the global mass distribution is taken into account.
477
- Choi, Seong-Hwan
- Journal of the Korean astronomical society = 천문학회지
- 38, n.4
- pp.463-470
- 2005
- 원문 바로보기
In this paper, we have made the component-based development of observational software for KASI solar imaging spectrograph (KSIS) that is able to obtain three-dimensional imaging spectrograms by using a scanning mirror in front of the spectrograph slit. Since 2002, the KASI solar spectrograph has been successfully operated to observe solar spectra for a given slit region as well as to inspect the response functions of narrow band filters. To improve its capability, we have developed the KSIS that can perform sequential observations of solar spectra by simultaneously controlling the scanning mirror and the CCD camera via Visual C++. Main task of this paper is to introduce the development of the component-based software for KSIS. Each component of the software is reusable on the level of executable file instead of source code because the software was developed by using CBD (component-based development) methodology. The main advantage of such a component-based software is that key components such as image processing component and display component can be applied to other similar observational software without any modifications. Using this software, we have successfully obtained solar imaging spectra of an active region (AR 10708) including a small sunspot. Finally, we present solar <TEX>$H{\alpha}$</TEX> spectra (<TEX>$6562.81{\AA}$</TEX>) that were obtained at an active region and a quiet region in order to confirm the validity of the developed KSIS and its software.
478
- SATO BUN'EI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.315-318
- 2005
- 원문 바로보기
We have carried out a precise Doppler survey of G-type giants aiming to unveil the properties of planetary systems in intermediate-mass stars (<TEX>$1.5-5M_{\bigodot}$</TEX>). G-type giants are promising targets for Doppler planet searches around massive stars, because they are slow-rotators and have many sharp absorption lines in their spectra and their surface activities are relatively low in contrast to their younger counterparts on the main-sequence (B-A stars). We are now monitoring radial velocities of about 300 late G-type (including early K-type) giants using HIgh Dispersion Echelle Spectrograph (HIDES) at Okayama Astrophysical Observatory. We have achieved a Doppler precision of about 6-7 m/s over a time span of 3 years using an iodine absorption cell. We found that most of the targets have radial velocity scatters of <TEX>${\sigma}{\~} 10-20 m\;s^{-1}$</TEX> over 1-3 years, with the most stable reaching levels of 6-8 m <TEX>$s^{-1}$</TEX>. Up to now, we have succeeded in discovering the first extrasolar planet around a G-type giant star HD 104985, and also found several candidates showing significant radial velocity variations, suggesting the existence of stellar and substellar companions. Observations have continued to establish their variability.
479
- LIM JEREMY
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.237-240
- 2005
- 원문 바로보기
We present images of L1551 IRS5 at angular resolutions as high as <TEX>${\~}$</TEX>30 mas, corresponding to a spatial resolution of <TEX>${\~}$</TEX>5 AU, made at 7 mm with the VLA. Previously known to be a binary protostellar system, we show that L1551 IRS5 is likely a triple protostellar system. The primary and secondary components have a projected separation of <TEX>${\~}$</TEX>46 AU, whereas the tertiary component has a projected separation of <TEX>${\~}$</TEX>11 AU from the primary component. The circumstellar dust disks of the primary and secondary components have dimensions of <TEX>${\~}$</TEX>15 AU, whereas that of the tertiary component has a dimension of <TEX>${\~}$</TEX>10 AU. Their major axes are closely, but not perfectly, aligned with each other, as well as the major axis of the surrounding flattened, rotating, and contracting molecular condensation (pseudodisk). Furthermore, the orbital motion of the primary and secondary components is in the same direction as the rotational motion of this pseudodisk. We suggest that all three protostellar components formed as a result of the fragmentation of the central region of the molecular pseudo disk. The primary and secondary components, but apparently not the tertiary component, each exhibits a bipolar ionized jet that is centered on and which emergers perpendicular to its associated dust disk. Neither jets are resolved along their base, implying that they are driven within a radial distance of <TEX>${\~}$</TEX>2.5 AU from their central protostars. Finally, we show evidence for what may be dusty matter streams feeding the two main protostellar components.
480
- Bong, Su-Chan
- Journal of the Korean astronomical society = 천문학회지
- 38, n.4
- pp.445-462
- 2005
- 원문 바로보기
In a companion paper, we have presented so-called Spatio-Spectral Maximum Entropy Method (SSMEM) particularly designed for Fourier-Transform imaging over a wide spectral range. The SSMEM allows simultaneous acquisition of both spectral and spatial information and we consider it most suitable for imaging spectroscopy of solar microwave emission. In this paper, we run the SSMEM for a realistic model of solar microwave radiation and a model array resembling the Owens Valley Solar Array in order to identify and resolve possible issues in the application of the SSMEM to solar microwave imaging spectroscopy. We mainly concern ourselves with issues as to how the frequency dependent noise in the data and frequency-dependent variations of source size and background flux will affect the result of imaging spectroscopy under the SSMEM. We also test the capability of the SSMEM against other conventional techniques, CLEAN and MEM.