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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of The Korean Astronomical Society
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The Korean Astronomical Society
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Volume & Issues
Volume 22, Issue 2 - Dec 1989
Volume 22, Issue 1 - Jun 1989
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STELLAR POPULATIONS IN EXTERNAL GALAXIES
Whang, Yun-Oh ; Lee, Sang-Gak ;
Journal of The Korean Astronomical Society, volume 22, issue 1, 1989, Pages 1~24
By applying population synthesis method, stellar populations in the nuclei of M31 and M32 are studied. We obtained five and four models for M31 and M32 respectively, for different main sequence turn-offs and keeping the astrophysical constraints as loose as possible. The best models for M31 and M32 are thought to have G0-5 and F5-8 main sequence trun-offs respectively. These models show that the main sequence stars outnumber the giants, which indicates the dwarf-dominance in external galactic nuclei. Even though there are some computational difficulties because of non-uniqueness in solution, two major points can be pointed out when compared to the previous papers. First, the ultraviolet deficiency expected from the conventional metal rich population models is not detected in our models, Instead ultraviolet radiation turns out to be somewhat higher than that of observation. Second one is the minor contribution from the Super Metal Rich (SMR) K giants to the integrated light of the program galaxies. That is, in our models, the SMR contribution is at best the same level as normal giants contrary to the SMR dominance of previous models. Since the loose astrophysical constraints are the major difference of our study from the previous ones, one should re-examine carefully for their validity further.
CO OBSERVATIONS OF A HIGH VELOCITY CLOUD
Kim, K.T. ; Mihn, Y.C. ; Hasegawa, T.I. ;
Journal of The Korean Astronomical Society, volume 22, issue 1, 1989, Pages 25~30
We report a null detection of
emission from a sub-condensation in a High Velocity Cloud (HVC). As a consequence of this, an upper limit of
was set. This implies that
abundance is deficient by at least a factor of 10 if the HVC is predominantly molecular, otherwise the CO abundance of the HVC might be normal.
SURFACE BRIGHTNESS AND MASS DISTRIBUTION OF THE LATE TYPE SPIRAL GALAXY NGC 2403
Lee, Yoo-Mi ; Chun, Mun-Suk ;
Journal of The Korean Astronomical Society, volume 22, issue 1, 1989, Pages 31~41
Luminosity profile of the late type spiral galaxy NGC 2403 was obtained using the PDS scan of the plate. Some physical parameters (scale length, total magnitude, central brightness, disk to bulge ratio and concentric indices) were calculated from the brightness distribution. Total mass and the mass to luminosity ratio were estimated from the fitting of various mass models.
THE AGE-METALLICITY RELATION FOR FIELD DISK STARS IN THE SOLAR NEIGHBORHOOD
Lee, See-Woo ; Ann, Hong-Bae ; Sung, Hwan-Kyung ;
Journal of The Korean Astronomical Society, volume 22, issue 1, 1989, Pages 43~61
The ages of field stars given in the catalogue of Cayrel de Strobel et al. (1985) are derived by the five different methods with combination of theoretical isochrones. By using these ages and metal abundances homogenized by Lee and Choe (1988), the age-metallicity relations are obtained. For disk stars of [Fe/H] > -0.9, the present age-metallicity relations are nearly consistent with those given by Twarog (1980) and Carlberg et al. (1985).
DETERMINATION OF THE DISTANCE TO B 361 BY A MODIFIED VERSION OF THE WOLF DIAGRAM
Hong, S.S. ; Sohn, D.S. ;
Journal of The Korean Astronomical Society, volume 22, issue 1, 1989, Pages 63~79
Current estimates, based on the same star-count analysis, of the distance to the globule Bamard 361 range from 300 pc to 650 pc. All the problems associated with the estimates have been fully rectified in this study, and a modification has been made to the classical Wolf diagram to improve the accuracy in the distance determination. A reference field was carefully selected close to the globule but well outside the globule boundary, and star counts for this field were performed on the blue POSS plate in order to set up the reference magnitude sequence appropriate to the general area of B 361. From the reference sequence, the stellar density function has been derived specifically for the direction toward the globule. Correction was made for the general interstellar extinction, and the luminosity function with the Wielen's dip was adopted. The resulting density function clearly reveals the existence of the local Cygnus-Orion arm in the direction of B 361 at about 700 pc away from the Sun. Analysis of the star-count data for the program field locates the globule at distance
pc ; thus, the globule is an object located in the Cygnus-Orion arm, residing somewhat toward its leading edge.