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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 54/122
531
- SOHN J,
- Journal of the Korean astronomical society = 천문학회지
- 37, n.4
- pp.261-263
- 2004
- 원문 바로보기
We present a progress report on HCN(1-0) line observations toward starless cores to probe inward motions. We have made a single pointing survey toward the central regions of 85 starless cores and performed mapping observations of 6 infall candidate starless cores. The distributions of the velocity difference between HCN(1-0) hyperfine lines and the optically thin tracer <TEX>$N_2H^+$</TEX>(1-0) are significantly skewed to the blue, meaning that HCN(1-0) frequently detects inward motions. Their skewness to the blue is even greater than that of CS(2-1) Lee et al., possibly implying more infall occurrence than CS(1-0). We identify 19 infall candidates by using several characteristics illustrating spectral infall asymmetry seen in HCN(1-0) hyperfine lines, CS(3-2), CS(2-1), <TEX>$DCO^+(2-1)$</TEX> and <TEX>$N_2H^+$</TEX> observations. The HCN(1-0) F(O-l) with the least optical depth usually shows a similar intensity distribution to that of <TEX>$N_2H^+$</TEX> which closely traces the density distribution of the cores, indicating that HCN(1-0) is less chemically affected and so believed to reflect kinematics occurring in rather inner regions of the cores. Detailed radiative transfer model fits of the spectra are underway to analyze central infall kinematics in starless cores.
532
- KURTZ S.
- Journal of the Korean astronomical society = 천문학회지
- 37, n.4
- pp.265-268
- 2004
- 원문 바로보기
Molecular clouds present many levels of structure, including clumps and cores of varying size and density. We present a brief summary of these cores, describing their observed physical properties and their place in the star formation process. We conclude with some speculation about pre-proto-stellar stages of molecular cores and the observational challenges in their observation.
533
- HENRY J. PATRICK
- Journal of the Korean astronomical society = 천문학회지
- 37, n.5
- pp.371-374
- 2004
- 원문 바로보기
We review the observational evidence for the existence of a warm-hot intergalactic medium (WHIM). We expect that the morphology of this material is similar to that of cosmic rays and magnetic fields in large-scale structure, i.e., filaments connecting clusters of galaxies. Direct evidence for the WHIM, either in emission or absorption, is weak.
534
- KOO BON-CHUL
- Journal of the Korean astronomical society = 천문학회지
- 37, n.2
- pp.61-77
- 2004
- 원문 바로보기
We have searched for HI 21 cm line emission from shocked atomic gas associated with southern supernova remnants (SNRs) using data from the Southern Galactic Plane Survey. Among the 97 sources studied, we have detected 10 SNRs with high-velocity HI emission confined to the SNR. The large velocity and the spatial confinement suggest that the emission is likely from the gas accelerated by the SN blast wave. We also detected 22 SNRs which show HI emission significantly brighter than the surrounding regions over a wide (<TEX>$>10 km\;s^{-1}$</TEX>) velocity interval. The association with these SNRs is less certain. We present the parameters and maps of the excess emission in these SNRs. We discuss in some detail the ten individual SNRs with associated high-velocity HI emission.
535
- MAZZOTTA PASQUALE
- Journal of the Korean astronomical society = 천문학회지
- 37, n.5
- pp.381-385
- 2004
- 원문 바로보기
Similarly to other cluster of galaxies previously classified as cooling flow systems, the Chandra observation of MKW 3s reveals that this object has a complex X-ray structure hosting both a X-ray cavity and a X-ray filament. Unlike the other clusters, however, the temperature map of the core of MKW 3s shows the presence of extended regions of gas heated above the radially averaged gas temperature at any radius. As the cluster does not show evidences for ongoing major mergers Mazzotta et al. suggest a connection between the heated gas and the activity of the central AGN. Nevertheless, due to the lack of high quality radio maps, this interpretation was controversial. In this paper we present the results of two new radio observations of MKW 3s at 1.28 GHz and 604 MHz obtained at the GMRT. Together with the Chandra observation and a separate VLA observation at 327 MHz from Young, we show unequivocal evidences for a close connection between the heated gas region and the AGN activity and we briefly summarize possible implications.
536
- KIM S.-J.
- Journal of the Korean astronomical society = 천문학회지
- 37, n.1
- pp.55-59
- 2004
- 원문 바로보기
We have developed a two fluid solar wind model from the Sun to 1 AU. Its basic equations are mass, momentum and energy conservations. In these equations, we include a wave mechanism of heating the corona and accelerating the wind. The two fluid model takes into account the power spectrum of Alfvenic wave fluctuation. Model computations have been made to fit observational constraints such as electron(<TEX>$T_e$</TEX>) and proton(<TEX>$T_p$</TEX>) temperatures and solar wind speed(V) at 1 AU. As a result, we obtained physical quantities of solar wind as follows: <TEX>$T_e$</TEX> is <TEX>$7.4{\times}10^5$</TEX> K and density(n) is <TEX>$1.7 {\times}10^7\;cm^{-3}$</TEX> in the corona. At 1 AU <TEX>$T_e$</TEX> is <TEX>$2.1 {\times} 10^5$</TEX> K and n is <TEX>$0.3 cm^{-3}$</TEX>, and V is <TEX>$511 km\;s^{-1}$</TEX>. Our model well explains the heating of protons in the corona and the acceleration of the solar wind.
537
- KWON S. M.
- Journal of the Korean astronomical society = 천문학회지
- 37, n.4
- pp.179-184
- 2004
- 원문 바로보기
We have developed a wide-field imaging camera system, called WICZO, to monitor light of the night sky over extended period. Such monitoring is necessary for studying the morphology of interplanetary dust cloud and also the time and spatial variations of airglow emission. The system consists of an electric cooler a CCD camera with <TEX>$60\%$</TEX> quantum efficiency at 500nm, and a fish-eye lens with <TEX>$180^{\circ}$</TEX> field of view. Wide field imaging is highly desired in light of the night sky observations in general, because the zodiacal light and the airglow emission extend over the entire sky. This paper illustrates the design of WICZO, reports the result of its laboratory performance test, and presents the first night sky image, which was taken, under collaboration with Byulmaro Observatory, on top of Mt. Bongrae at Yongweol in January, 2004.
538
- KUWABARA TAKUHITO
- Journal of the Korean astronomical society = 천문학회지
- 37, n.5
- pp.601-603
- 2004
- 원문 바로보기
We present the results of the linear analysis for the Parker-Jeans instability in the magnetized gas disks including the effect of cosmic-ray diffusion along the magnetic field lines. We adopted an uni-formly rotating two temperature layered disk with a horizontal magnetic fields and solved the perturbed equations numerically. Fragmentation of gases takes place and filamentary structures are formed by the growth of the instability. Nagai et al. (1998) showed that the direction of filaments being formed by the Parker-Jeans instability depends on the strength of pressure outside the unperturbed gas disk. We found that at some range of external pressures the direction of filaments is also governed by the value of the diffusion coefficient of CR along the magnetic field lines k.
539
- FERETTI L.
- Journal of the Korean astronomical society = 천문학회지
- 37, n.5
- pp.315-322
- 2004
- 원문 바로보기
Several arguments have been presented in the literature to support the connection between radio halos and cluster mergers. The spectral index distributions of the halos in A665 and A2163 provide a new strong confirmation of this connection, i.e. of the fact that the cluster merger plays an important role in the energy supply to the radio halos. Features of the spectral index (flattening and patches) are indication of a complex shape of the radiating electron spectrum, and are therefore in support of electron reacceleration models. Regions of flatter spectrum are found to be related to the recent merger. In the undisturbed cluster regions, instead, the spectrum steepens with the distance from the cluster center. The plot of the integrated spectral index of a sample of halos versus the cluster temperature indicates that clusters at higher temperature tend to host halos with flatter spectra. This correlation provides further evidence of the connection between radio emission and cluster mergers.
540
- KRONBERG PHILIPP P.
- Journal of the Korean astronomical society = 천문학회지
- 37, n.5
- pp.343-347
- 2004
- 원문 바로보기
The energy injection of galactic black holes (BH) into the intergalactic medium via extragalactic radio source jets and lobes is sufficient to magnetize the IGM in the filaments and walls of Large Scale Structure at < [B] > <TEX>${\~}0.l{\mu}G$</TEX> or more. It appears that this process of galaxy-IGM feedback is the primary source of IGM cosmic rays(CR) and magnetic field energy. Large scale gravitational infall energy serves to re-heat the intergalactic magnetoplasma in localities of space and time, maintaining or amplifying the IGM magnetic field, but this can be thought of as a secondary process. I briefly review observations that confirm IGM fields around this level, describe further Faraday rotation measurements in progress, and also the observational evidence that magnetic fields in galaxy systems around z=2 were approximately as strong then, <TEX>${\~}$</TEX>10 Gyr ago, as now.