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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Publications of The Korean Astronomical Society
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The Korean Astronomical Society
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Volume 7, Issue 1 - Dec 1992
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COSMOLOGY, EPISTEMOLOGY AND CHAOS
Unno, Wasaburo ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 1~7
We may consider the following three fundamental epistemological questions concerning cosmology. Can cosmology at last understand the origin of the universe? Can computers at last create? Can life be formed at last synthetically? These questions are in some sense related to the liar paradox containing the self-reference and, therefore. may not be answered by recursive processes in finite time. There are, however. various implications such that the chaos may break the trap of the self-reference paradox. In other words, Goedel's incompleteness theorem would not apply to chaos, even if the chaos can be generated by recursive processes. Internal relations among cosmology, epistemology and chaos must be investigated in greater detail.
LARGE-SCALE CLUSTERING OF GALAXIES IN THE CFA SURVEY
Park, Chang-Bom ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 9~17
The power spectrum of the galaxy distribution is accurately measured up to wavelengths over
Mpc from the CfA 1 and 2 catalogs. We find that our results agree with power spectra calculated by others from smaller samples of optical, radio and infrared galaxies. The power spectrum of an open CDM model (
= 0.2 and
= 1; see below for definitions) best approximates the observed power spectrum. The power spectrum of the standard COM model (
= 0.5 and
= 1) is inconsistent with the observed one at the 99% confidence level. Our best estimation of the corresponding correlation function in real space is
for r <
CAN THE UNIVERSE BE "TILTED"?
La, Daile ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 19~23
We investigated the "tilting" of the Universe, i.e., a non-Doppler origin of the dipole moment of the cosmic background radiation (CBR). Superhorizon-sized isocurvature, rotational and true vacuum bubble perturbations are considered. We show that the more natural way of the "tilting" the Universe is via the true vacuum bubble perturbation. Nevertheless, due to the small filling fraction of the bubbles of viable extended inflationary models, we find that the probability of the real occurrence in the Universe is quite insignificant.
GALAXY CORRELATION IN A BUBBLY UNIVERSE
Ryu, Dong-Su ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 25~30
Recent redshift surveys suggest that most galaxies may be distributed on the surfaces of bubbles surrounding large voids. To investigate the quantitative consistency of this qualitative picture of large-scale structure, we study analytically the clustering properties of galaxies in a universe filled with spherical shells. In this paper, we report the results of the calculations for the spatial and angular two-point correlation functions of galaxies. With
of galaxies in clusters and a power law distribution of shell sizes,
, the observed slope and amplitude of the spatial two-point correlation function
can be reproduced. (It has been shown that the same model parameters reproduce the enhanced cluster two-point correlation function,
). The corresponding angular two-point correlation function
is calculated using the relativistic form of Limber's equation and the Schecter-type luminosity function. The calculated w(
) agrees with the observed one quite well on small separations (
DARK MATTER IN THE UNIVERSE : BRIEF REVIEW
Oh, Kap-Soo ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 31~37
Dark matter in various size of scales is reviewed briefly. The evidence of dark matter in dwarf spheroidal galaxies is still uncertain. However there is no doubt about the existence of dark matter in larger scales. Many proposed candidates for dark matter are still speculative. Several possibilities of direct detection of dark matter are proposed.
DISCOVERY OF VELOCITY INHOMOGENEITIES IN THE COMA, HYDRA, ABELL 2256 CLUSTER OF GALAXIES
Kim, Kwang-Tae ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 39~50
A velocity inhomogeneity, which is the regional preponderence of either radial or tangential orbits, is searched with the new technique proposed by Kim (1992) for Coma, Hydra I, and Abell 2256 cluster of galaxies. Conspicuous inhomogeneities are found in the Coma and A2256 which X-ray isophotes are indicative for their underlying potentials being ellipitcal in shape, Even in their central regions, zones that are dominated by radial orbits are clearly distinguishable from that of the tangential orbits, and defining the cluster 'equator' as the direction of maximum elongation of the X-ray isophotes, radial orbits dominate along this direction whereas tangential orbits dominate the 'polar' zones. Merger events that are evidenced in X-ray observations occur in the equatorial zones of Coma and A2256, suggesting preponderence of radial orbits in the zones, which is in good agreement with their velocity structures. On the other hand, the inhomogeneity in Hydra I turns out to be insignificant in the central regions and this is just what is expected from a cluster whose X-ray isophotes is nearly circular. The velocity distribution in regions further out, however, shows significant inhomogeneity and this seems to support the previous results that this cluster is likely to have substructures and velocity anisotropy.
STOCHASTIC SCALING EFFECT AND STATISTICS OF COSMOLOGICAL DENSITY FLUCTUATIONS
Yi, In-Su ; Vsihniac, Ethan T. ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 51~61
The nonlinear stochastic behavior of chaotic inflation is characterized by the 'scaling' effect. Using a simple criterion for the appearance of scaling behavior in the
inflation model, we show explicitly that in this limit the onset of the scaling regime does not require any special initial conditions and that it is independent of the self-coupling constant
. Non-Gaussian statistics in adiabatic fluctuations are important only for super-horizon scales and the scaling regime does not lead to any significant statistical properties on currently observable scales. However, the scaling effect gives some cosmological consequences very different from what we expect in the naive diffusion approximation for quantum fluctuations. The classical (deterministic) treatment of the inflation field (essentially a quantum mechanical object.) becomes valid towards the end of inflation.
THE X-RAY EMISSION FROM EARLY TYPE GALAXIES
Kim, Dong-Woo ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 63~69
We have systematically investigated the X-ray spectra of normal galaxies, by using the Imaging Proportional Counter (IPC) data in the Einstein data base. We employed the X-ray color-color plot as well as the standard model fitting method which requires higher signal to noise ratio. We discuss X-ray emission mechanisms in terms of their spectral properties and the signature of cooling flows which are most likely present in X-ray bright early type galaxies. On the average, fits to absorbed thermal spectra show that the X-ray emission temperature of spirals is higher than that of ellipticals. This is consistent with our understanding that accreting binaries are a major X-ray source in spirals, while extended gaseous halos are present in ellipticals. The emission temperature becomes lower with increasing X-ray to optical luminosity ratio in E and S0 galaxies. This result is what we would expect if the emission of X-ray faint early type galaxies consists of a large evolved stellar component, while the gaseous emission becomes dominant in X-ray brighter galaxies. We also find a cool, self-absorbed core in some early type galaxies, which directly indicates the presence of cooling flows in such galaxies.
MAGNETOHYDRODYNAMIC WAVE PROPAGATION IN THE "IONOSPHERE" OF THE CENTRAL BLACK HOLE IN AN ACTIVE GALACTIC NUCLEUS
Park, Seok-Jae ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 71~77
An axisymmetric, stationary electrodynamic model of the central engine of an active galactic nucleus has been well formulated by Macdonald and Thorne. In this model the relativistic region around the central black hole must be filled by highly conducting plasma and the equations of magnetohydrodynamics are then satisfied. In this paper we analyze magnetohydrodynamic wave propagation in this region. We find that there are three distinct types of waves - the Alfven wave and two magnetosonic waves. The wave equations turn out to be not very different from those in nonrelativistic case except they are redshifted.
GRAVITATIONAL LENSING AND THE GEOMETRY OF THE UNIVERSE
Park, Myeong-Gu ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 79~87
New and improved data on the gravitational lens systems discovered so far are compared with the theoretical predictions of Gott, Park, and Lee (1989, GPL). Systems lensed by a single galaxy, compatible with assumptions of GPL, support flat or near-flat geometry for the universe. But the statistical uncertainty is too large to draw any definite conclusion. We need more lens systems. Also, the probability of multiple image lensing and mean separation of the images averaged over the source distribution are calculated for various cosmological models. Multiple-image lens systems and radio ring systems are compared with the predictions. Although the data reject exotic cosmological models, it cannot discriminate among conventional Friedmann models yet.
BLACK HOLES IN GALACTIC NUCLEI: ALTERNATIVES AND IMPLICATIONS
Lee, Hyung-Mok ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 89~96
Recent spectroscopic observations indicate concentration of dark masses in the nuclei of nearby galaxies. This has been usually interpreted as the presence of massive black holes in these nuclei. Alternative explanations such as the dark cluster composed of low mass stars (brown dwarfs) or dark stellar remnants are possible provided that these systems can be stably maintained for the age of galaxies. For the case of low mass star cluster, mass of individual stars can grow to that of conventional stars in collision time scale. The requirement of collision time scale being shorter than the Hubble time gives the minimum cluster size. For typical conditions of M31 or M32, the half-mass radii of dark clusters can be as small as 0.1 arcsecond. For the case of clusters composed of stellar remnants, core-collapse and post-collapse expansion are required to take place in longer than Hubble time. Simple estimates reveal that the size of these clusters also can be small enough that no contradiction with observational data exists for the clusters made of white dwarfs or neutron stars. We then considered the possible outcomes of interactions between the black hole and the surrounding stellar system. Under typical conditions of M31 or M32, tidal disruption will occur every
years. We present a simple scenario for the evolution of stellar debris based on basic principles. While the accretion of stellar material could produce large amount of radiation so that the mass-to-light ratio can become too small compared to observational values it is too early to rule out the black hole model because the black hole can consume most of the stellar debris in time scale much shorter than mean time between two successive tidal disruptions. Finally we outline recent effort to simulate the process of tidal disruption and subsequent evolution of the stellar debris numerically using Smoothed Particle Hydrodynamics technique.
GRAVITATIONAL MICRO-LENSING EFFECTS AND ASTROPHYSICAL APPLICATIONS
Chang, Kyong-Ae ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 97~105
The most favourable possibilities to observe the phenomena of gravitational lensing are the high amplification events and the time delay between the images. These effects provide us the information to determine the Hubble parameter and the matter distribution in the universe. The image properties due to micro-lensing also is of an importance to find out the size and the structure of the source.
NEWTONIAN COSMOLOGICAL PERTURBATIONS
Hwang, Jai-Chan ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 107~148
This paper presents a cosmological perturbation analysis in a Newtonian framework, using the Newtonian multi component version of the relativistic covariant equations. This work considers the fully nonlinear evolution of the perturbations, and is generalized to multicomponent systems and imperfect fluids. Known nonlinear solutions are presented in a general framework. Quasi-nonlinear analysis, considering both the compressible and rotational modes, is presented, including cases already known in the literature. The Fourier space representation of the conservation equations is also derived in a general context, with various decompositions of the velocity field. Commonly accepted cosmogonical frameworks are critically examined in the context of nonlinear evolution. This work may be regarded as the Newtonian counterpart of a recently presented general relativistic covariant formulation.
대덕전파천문대 13.7 M 전파망원경의 효율
Kim, Bong-Gyu ; Jeong, Jae-Hun ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 149~153
We determined the efficiencies of the aperture. beam and forward spillover and scattering of 13.7 m radio telescope at Daeduk Radio Astronomy Observatory through the observations of the planets and Moon. The main panels adjustments were carried out on September 1991 and the improvements in the efficiencies were checked by comparing the observations made before and after the panel adjustments. The efficiencies were turned out to be 0.35, 0,47 and 0.83 at 115.27 GHz for the aperture, beam and forward scattering and spillover. respectively. These marked nearly a factor of two upgrade of the efficiencies previously measured.
만기형 변광성들에 대한 SiO 메이저선 관측
Kim, Bong-Gyu ; No, Deok-Gyu ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 155~166
We observed a total of 14 Mira variables as well as 4 late type variable stars for their SiO
, J = 2 - 1 maser lines from April 1989 to November 1990 with the 13.7 m radio telescope at Daeduk Radio Astronomy Observatory. The maser intensity variations were the prime objective of the observations which well covered the periods of the variations. The origion of the variations were studied by comparing wi th those previousely measured in optical and infrared(IR) wavelengths and we confirmed that the intensity variations were in good correlation with those in V magnitude and IR intensity as previousely found in former investigators in general. However, for a few sources, we could find the missing maxima. The intensities themselves also were in good correlation with SiO
, J = 1 - 0 maser intensities observed in Yebes as expected. The good correlations indicate that the pumping source of the SiO maser is likely to be the IR emission in the masing regions and the "missing maxima" that are apparent in two particular sources are considered to relate wi th the strength of shocks arising from the eruptive mass-loss from central stars.
SNU WASHINGTON 측광계의 표준화와 WASHINGTON 측광계의 일반적 특성
An, Seong-Min ; Lee, Si-U ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 167~188
사진 건판의 초증감 처리 장치의 제작 (II)
Jeon, Yeong-Beom ; Sim, Gyeong-Jin ; Kim, Gang-Min ; Cheon, Mu-Yeong ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 189~205
FIELD RR LYRAE 변광성의 특성: 공간분포 및 증원소함량 분포
Jeon, Yeong-Beom ; Lee, Si-U ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 207~229
우리 은하의 적외선 모형 II
Gang, Yong-Hui ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 231~253
A model for the distribution of stars in the disk and the spheroid of our Galaxy is reexamined from an edge-on view of the Galaxy obtained by selecting infrared sources from the IRAS Point Source Catalog. The sources are counted as a function of galactic latitude. longitude and
apparent magnitude. The source counts are reasonably separated into the disk component and the spheroid component contributions and each of the contributions is further interpreted as a convolution of a spatial density distribution and a luminosity function based on the least-square fit method. The spatial density of the disk component has an exponential radial scale length of
and the vertical distribution follows a canonical
law with a scale height
. The distribution of the spheroid component can be represented by an oblate spheriod with an axis ratio
and a de Vaucouleurs'
law with an effective radius of
. The steep density gradient of the spheroid component is consistent with that of late M giants in the central bulge. The luminosity functions of the disk and the spheroid component stars resemble respectively those of the K luminosity function of disk M giants (Garwood and Jones 1986) and the bolometric luminosity function of M giants in bulge fields (Frogel et al, 1990).
1992년 흑점 상대수
Sim, Gyeong-Jin ; Park, Yeong-Deuk ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 255~260
천체화상처리용 그래픽 라이브러리
Kim, Gap-Seong ; Hong, Seung-Su ;
Publications of The Korean Astronomical Society, volume 7, issue 1, 1992, Pages 261~271