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- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,187건 (DB Construction : 1,187 Articles)
총 게시글 1,187건
페이지 76/119
751
- CHOE G. S.
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.89-93
- 1998
- 원문 바로보기
An attempt is made to find the boundary tangential components of potential magnetic fields without constructing solutions in the entire domain. In our procedure, the magnetic energy is expressed as a functional of tangential and normal magnetic fields at the boundary and is minimized by the variational principle. This paper reports a preliminary study on two dimensional potential fields above a plane.
752
- LEE KANG HWAN
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.101-104
- 1998
- 원문 바로보기
We have obtained photometry of stars in NGC 2264 with several combinations of H<TEX>$\alpha$</TEX> filters and continuum filters. The main purpose of these observations was to determine the best filter combination for selecting low ma!,s member stars in their Pre-Main Sequence (PMS) stage using H<TEX>$\alpha$</TEX> photometry. A narrow band H<TEX>$\alpha$</TEX> filter (<TEX>${\Delta}{\lambda}$</TEX> = <TEX>$l0{\AA}$</TEX>) with any combination of continuum filters showed the highest resolution in the H<TEX>$\alpha$</TEX> photometry.
753
- LEE HYUNG MOK
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.95-99
- 1998
- 원문 바로보기
We report preliminary results of an on-going survey of optically selected barred galaxies with <TEX>$^{12}CO$</TEX>(J=1-0) line. The entire sample is composed of about 100 bright barred galaxies (<TEX>$B_T{\le}13$</TEX>) with small inclination angle. Most of the galaxies are relatively nearby with receding speed less than 10,000 km/sec. In the first observing run, we have observed central parts of 18 galaxies and detected CO emissions from 5 galaxies (NGC521, 2525, 4262, 4900, and 7479). Most of these galaxies are not observed with CO previously, except for NGC7479 which has been studied at various wavelengths. The peak antenna temperature of detected galaxies ranges from about 30 to 300 mK.
754
- LEE KANG HWAN
- Journal of the Korean astronomical society = 천문학회지
- 31, n.1
- pp.19-26
- 1998
- 원문 바로보기
The wide field <TEX>$(\~20'\times20')$</TEX> CCD photometry has been performed for more than 4,000 stars over a whole region of NGC 362 which is located inside the SMC halo. The Color-Magnitude diagram (CMD) and luminosit function (LF) for red giant branch (RGB) stars are presented, discussing a distinct bump along the RGB and some blue stars appearing in the blue horizontal branch (BHB) and above BHB. The anomalous globular cluster NGC 362 with highly populated red horizontal branch (RHB) stars is compared with the another anomalous globular cluster NGC 288 with highly populated BHB stars. A metal-rich, young blue component and metal-'poor, old red component of the SMC halo stars are examined.
755
- KYEONG JAE-MANN
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.127-140
- 1998
- 원문 바로보기
With a large format near-infrared camera at the 2.2-m telescope on Mauna Kea Observatory, we performed J K near-infrared observations for the metal rich globular cluster NGC6712. This cluster lies near the galactic plane and therefore suffers heavy reddening. We present the near-infrared color-magnitude diagram and also derive the metallicity ([Fe/H] <TEX>${\~}-0.96{\pm}0.27$</TEX>) as well as its distance modulus ((m - M) <TEX>${\~}13.42{\pm}0.12$</TEX>).
756
- KIM MINSUN
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.109-115
- 1998
- 원문 바로보기
We show that the low density regions of the matter distribution preserve the properties of the primordial density field better than the high density regions. We have performed a cosmological N-body simulation of large-scale structure formation in the standard CDM cosmology, and studied the evolution of statistics of under-density and over-density regions separately. The rank-order of the under-density regions is closer to the original one compared to that of the over-density regions. The under-density peaks (or voids) has moved less than over-density peaks (or dense clusters of galaxies) from their initial positions. Therefore, the under-density regions are more useful than the over-density regions in the study of the statistical property of the primordial density field.
757
- KIM YONGCHEOL
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.77-87
- 1998
- 원문 바로보기
The accumulated knowledge of the influence of solar granulation on spectral lines, i.e. their asymmetry, provides a key to analyze stellar spectral line asymmetries. In this paper, a simple line synthesis using a simple 'model' of granulation was calculated. By adjusting the properties of the granule model, the observed imprints of convection on spectral lines can be reproduced. Since we depict convective flows using a continuous function rather than using a few components of flows (cf. Gray and Toner 1985, 1986; dravins 1990), we were able to identify which components of convection are important in line bisector shapes. The results of this study can be summarized as follows: Firstly, the intensity contrast (i.e. temperature fluctuation), and the area coverage of up- and down-flows are the two important factors which determine the line bisector shapes. Secondly, on the contrary to the assumption of other studies, the effect of horizontal flows is non-negligible. This exercise provides a qualitative understanding of the effect of convection on spectral lines. This knowledge serves as a guideline for understanding the characteristic difference in convection for stars on either side of the 'Granulation Boundary' (Gray 1982; Gray and Nagel 1989).
758
- PARK CHANGBOM
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.105-108
- 1998
- 원문 바로보기
We have found that the two-point correlation function of the APM clusters of galaxies has an amplitude much higher than that claimed by the APM group. As the richness limit increases from R = 53 to 80, the correlation length increases from 17.5 to 28.9 <TEX>$h^{-1}Mpc$</TEX>. This indicates that the richness dependence of the APM cluster correlation function is also much stronger than what the APM group has reported. The richness dependence can be represented by a fitting formula ro = 0.53dc + 0.01, which is consistent with the Bahcall's formula ro = 0.4dc. We have tried to find the possible reason for discrepancies. However, our estimates for the APM cluster correlation function are found to be robust against variation of the method of calculation and of sample definition.
759
- KIM SANG CHUL
- Journal of the Korean astronomical society = 천문학회지
- 31, n.1
- pp.51-65
- 1998
- 원문 바로보기
We present B VRI CCD surface photometry for the central <TEX>$(6'.35\times6'.35)$</TEX> regions of the dwarf elliptical galaxies NGC 185 and NGC 205 in the Local Group. Surface brightness profiles of NGC 185 (R<225') and NGC 205 (R<186') show excess components in the central regions. The colors of NGC 185 get bluer inward at R<25', while they remain constant at <TEX>$R\geq25'$</TEX>. The colors of NGC 205 get bluer inward at 1'<R<50', and remain flat outside. Our photometry, supplemented by the photometry based on the far-ultraviolet and visual images of the HST archive data, shows that there is an inversion of color at the very nucleus region (at about 1'). The implications of the redder color of the core part of the nucleus compared with neighboring regions are discussed. The amount of the excess components in the central regions of these galaxies is estimated to be <TEX>$\approx10^5\; L_\bigodot$</TEX>. Distributions of dust clouds in the central regions of the two galaxies are also investigated.
760
- CHO DONG HWAN
- Journal of the Korean astronomical society = 천문학회지
- 31, n.1
- pp.67-74
- 1998
- 원문 바로보기
The VI CCD photometry is made for stars in the globular cluster M22 down to <TEX>$V\approx19^m,\;I\approx18^m$</TEX>. In the color-magnitude diagram (CMD), red giant branch (RGB), asymtotic giant branch (AGB) and blue horizontal branch (BHB) are well defined. The luminosity functions (LF) of RGB, AGB and BHB stars are derived, discussing deficient gaps and bumps in the CMD. The anomalously wide RGB seen in the BV photometric system is found to disappear in the VI photometric system.