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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
- KIM TAEHYUN
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.145-148
- 2005
- 원문 바로보기
We present a photometric study of galaxies in the central regions of six nearby galaxy clusters at redshift z=0.0231<TEX>${\~}$</TEX>0.0951. We have derived BVI photometry of the galaxies from the CCD images obtained at the Bohyunsan Optical Astronomical Observatory (BOAO) in Korea, and JHKs photometry of the bright galaxies from the 2MASS extended source catalog. Comparing the galaxy photometry results with the simple stellar population model of Bruzual & Charlot (2003) in the optical & NIR color-color diagrams, we have estimated the ages and metallicities of early type galaxies. We have found that the observed galaxies had recent star-formation mostly 5 <TEX>${\~}$</TEX> 7 Gyrs ago but the spread in age estimation is rather large. The average metallicities are [Fe/H]=0.l<TEX>${\~}$</TEX>0.5 dex. These results support the hypothesis that large early type galaxies in clusters are formed via hierarchical merging of smaller galaxies.
472
- 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.
473
- LEE HYUNG MOK
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.333-334
- 2005
- 원문 바로보기
Astronomical research in Asian Pacific region has been growing rapidly in recent years. However, most important papers have been published in well established existing journals in US and Europe because we do not have high impact international journals in this region. I review the current trends of the local journals of East Asian countries and propose to establish a new regional journal by combining domestic journals.
474
- 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.
475
CURRENT STATUS OF THE INSTRUMENTS, INSTRUMENTATION AND OPEN USE OF OKAYAMA ASTROPHYSICAL OBSERVATORY
- YOSHIDA MICHITOSHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.117-120
- 2005
- 원문 바로보기
Current instrumentation activities and the open user status of Okayama Astrophysical Observatory (OAO) are reviewed. There are two telescopes in operation and one telescope under reforming at OAO. The 188cm telescope is provided for open use for more than 200 nights in a year. The typical over-subscription rate of observation proposals for the 188cm telescope is <TEX>${\~}$</TEX> 1.5 - 2. The 50cm telescope is dedicated to <TEX>$\gamma$</TEX>-ray burst optical follow-up observation and is operated in collaboration with Tokyo Institute of Technology. The 91cm telescope will become a new very wide field near-infrared camera in two years. The high-dispersion echelle spectrograph (HIDES) is the current primary instrument for the open use of the 188cm telescope. Two new instruments, an infrared multi-purpose camera (ISLE) and an optical low-dispersion spectrograph (KOOLS), are now under development. They will be open as common use instruments in 2006.
476
- 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.
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
- UMETSU KEIICHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.191-195
- 2005
- 원문 바로보기
We used Subaru observations of A1689 (z = 0.183) to derive an accurate, model-independent mass profile for the entire cluster, r<TEX>$\le$</TEX>2Mpc/h, by combining magnification bias and distortion measurements. The projected mass profile steepens quickly with increasing radius, falling away to zero at r<TEX>${\~}$</TEX>1.0Mpc/h, well short of the anticipated virial radius. Our profile accurately matches onto the inner profile, r <TEX>$\le$</TEX>200kpc/ h, derived from deep HST / ACS images. The combined ACS and Subaru information is well fitted by an NFW profile with virial mass, <TEX>$(1.93 \pm 0.20) {\times}10^{15} M_{\bigodot}$</TEX>, and surprisingly high concentration, <TEX>$C_{vir} = 13.7^{+1.4}_{-1.1}$</TEX>, significantly larger than theoretically expected (<TEX>$C_{vir} {\le}4$</TEX>), corresponding to a relatively steep overall profile. These results are based on a reliable sample of background galaxies selected to be redder than the cluster E/SO sequence. By including the faint blue galaxy population a much smaller distortion signal is found, demonstrating that blue cluster members significantly dilute the true signal for r <TEX>$\le$</TEX> 400kpc/ h. This contamination is likely to affect most weak lensing results to date.
479
- HIRANO NAOMI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.219-222
- 2005
- 원문 바로보기
We present the high-resolution (2'-4') images of the molecular envelopes surrounding the evolved stars, V Hya, VY CMa, and <TEX>${\pi}^1$</TEX> Gru observed with the Submillimeter Array. The CO J=2-1 and 3-2 images of the carbon star V Hya show that the circumstellar structure of this star consists of three kinematic components; there is a flattened disk-like envelope that is expanding with a velocity of <TEX>${\~}16 km\;s^{-1}$</TEX>, the second component is the medium-velocity wind having a deprojected velocity of 40-120 km <TEX>$s^{-l}$</TEX> moving along the disk plane, and the third one is the bipolar molecular jet having an extreme velocity of 70-185 km <TEX>$s^{-l}$</TEX>. The axis of this high velocity jet is perpendicular to the plane of the disk-like envelope. We found that the circumstellar structure of the S-star <TEX>${\pi}^1$</TEX> Gru traced by the CO J =2-1 resembles that of V Hya quite closely; the star is surrounded by the expanding disk-like envelope and is driving the medium-velocity wind along the disk plane. We also obtained the excellent images of VY CMa with the CO and <TEX>$^{13}CO$</TEX> J=2-1 and <TEX>$SO\;6_5-5_4$</TEX> lines. The maps of three molecular lines show that the envelope has a significant velocity gradient in the east-west direction, suggesting that the envelope surrounding VY CMa is also flattened and expanding along its radial direction. The high-resolution images obtained with the SMA show that some AGB stars are associated with the asymmetric mass loss including the equatorial wind and bipolar jet.
480
- 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.