간행물
천문학회지 KCI 등재 SCOPUS Journal of The Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
- 간기 반년간
- ISSN 1225-4614 (Print)2288-890X (Online)
- 수록기간 1968 ~ 2024
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 440DDC 520
권호리스트/논문검색
제30권 제2호 (1997년 10월) 8건
1.
1997.10
구독 인증기관 무료, 개인회원 유료
Observational trends of the Jovian UV aurora, obtained from the Goddard High Resolution Spectrograph(GHRS) on board the Hubble Space Telescope(HST), are explained by a simple two component model. The model consists of cool and warm components with temperatures of about 400 and 1000K, and with methane absorptions corresponding to column densities of 6-9e16/cm2 and no methane absorption, respectively. Three trends that (1) brighter UV spectra have lower temperatures, and (2) spectra with stronger methane absorption show lower temperatures, and (3) spectra with stronger methane absorption seem to be brighter, are accounted by combinations of two components with various filling factors and intensity ratios. The model implies that precipitating particles responsibie for the cool component have higher individual energy and stronger energy flux than those for the warm component. Estimation of GHRS aperture location on UV auroral images taken by the Wide Field Planetary Camera 2(WFPC2) suggests that the cool component may correspond to emission along the oval, and the warm component to diffuse features of UV emission. Preliminary comparison of images by the WFPC2 and those by H3+ 4 micrometer ground-based observations implies that the warm component causes both weak diffuse features of UV emission and bright H3+ emission in an area at lambda III - 150 deg. inside the northern oval.
4,000원
2.
1997.10
구독 인증기관 무료, 개인회원 유료
We examine the corecollapse times of isolated, two-mass-component star clusters using Fokker-Planck models. With initial condition of Plummer models, we find that the corecollapse times of clusters with M1/M2 >> 1 are well correlated with (N1/N2)^0.5 (m1/m2)^2 Trh, where (M1/M2) and (m1/m2) are the light to heavy component total and individual mass ratios, respectively, N1/N2 is the number ratio, and Trh is the initial half-mass relaxation time scale. We also find two-component cluster parameters that best match multi-component (thus more realistic) clusters with power-law mass functions.
4,000원
3.
1997.10
구독 인증기관 무료, 개인회원 유료
We present a near-infrared (K, J-K) color magnitude diagram(CMD) for the central region of a metal poor globular cluster NGC 6535. Our near-infrared data are combined with published optical BV data to construct (K, V-K) CMD. A new metallicity estimate is made by applying the relation between metallicity and MKo as proposed by Frogel, Cohen and Persson(1983). Our value is [Fe/H] = -1.66+-0.06, which is slightly higher than other results previously reported.
4,200원
4.
1997.10
구독 인증기관 무료, 개인회원 유료
The BV photographic photometry was made for 1714 stars (V < 19.5m) in NGC 6752, using 83 photoelectric stars and many secondary photographic standard stars over the area of 3.3' - 11.3' from the cluster center. Their data and finding chart are presented.
5,400원
5.
1997.10
구독 인증기관 무료, 개인회원 유료
A small ultraviolet telescope which can be established on a satellite of the Korean small satellite (KITSAT) series is proposed with a concept design. Possible scientific objectives are identified, and the basic structure and characteristics of the telescope are described. In order to overcome limitation of pointing and stabilization accuracy of the KITSAT, a system of secondary stabilization is designed at the focal plane, where both star-tracking CCD and science detector share a 1.2deg field of view. Star tracking information is fed to three-axis drivers that move the platform on which the star-tracking CCD and science detector are installed. The proposed stabilization system is light and efficient, in comparison with a standard system of stabilization that basically moves the whole telescope or satellite. With a good intensified CCD and second stabilization system, the telescope will achieve a limiting magnitude of 21 at 1600 angstrom, which is sufficient for observing a variety of celestial objects, such as hot stars, nebulae, galaxies with UV excess, and quasars.
4,000원
6.
1997.10
구독 인증기관 무료, 개인회원 유료
We analyzed the luminosity profiles of 104 bright barred galaxies to examine the frequency of occurrence of the Type II disk which is thought to be the result of redistribution of disk material by bar potential. Our analysis of the elliptically averaged major axis profiles shows that about 70% of the present sample seem to have Type II disks with a weak tendency of preferential occurrence of type II disks in the late type galaxies. there is a subgroup of Type II disks which is characterized by a flat luminosity distribution in the middle disk, followed by a steep decline in the outer parts. Most of the galaxies with strong bars tend to have Type II disks. The present study strongly suggests that Type II disk is an evidence for the secular evolutions in disk galaxies.
4,900원
7.
1997.10
구독 인증기관 무료, 개인회원 유료
The luminosity function (LF) and present day mass function(PDMF) for main sequence (MS) stars in the Praesepe and Hyades clusters are derived, showing the Wielen Dip which occurs at Mv = 9m in the LF. This dip is about 2 mag fainter than the case for the Pleiades cluster whose Wielen Dip position is consistent with that for the solar neighborhood field stars. The Wielen Dips of these clusters are reproduced by using a bimodal initial mass function (IMF).
4,000원
8.
1997.10
구독 인증기관 무료, 개인회원 유료
We have developed a cosmological N-body code which can simulate unprecedently large number of massive particles. This code is based on the Particle-Mesh scheme, and utilize the recent fast I/O devices to swap all variables. Using the new code we have simulated the formation and evolution of structures at high redshifts in the standard Cold Dark Matter (CDM) cosmogony. A simulation evolving 1024^3 particles on a 2048^3 mesh with the initial standard CDM power spectrum is being made. This is the first billion particle cosmological simulation with initial conditions representing the theoretical model over the widest range of space. A smaller, but still very large CDM simulation with 512^3 particles on a 1024^3 mesh has been completed. We have found that the galaxy-scale CDM halos with diameters of tens of kpcs undergo complete collapse before redshift 10. Our results clearly indicate that galactic and subgalactic structures have formed far before redshift 5 which is the present upper limit to the epoch of observed structures. We emphasize that the non-linear evolution of the galactic and subgalactic-scale structures starts as early as z ~ 50, and that cosmological simulations must start at such high redshifts. A high mass resolution is also indispensable to accurately represent the theoretical model in the initial conditions down to subgalactic scales, and to correctly study the subsequent formation and evolution of structures through hierarchical clustering.
4,000원
