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        검색결과 4

        1.
        2001.10 구독 인증기관·개인회원 무료
        2.
        2001.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this paper, we investigate the correlation between the radial ultraviolet color distribution and the shapes of the ultraviolet isophote for elliptical galaxies (M32, NGC 1399) and spiral bulges (of M31, M81) by using their archival UIT images. For M31, M81, and NGC 1399, the radial ultraviolet color distributions show a two-component trend; as the distance from the galactic center increase the color becomes redder in the inner region while it becomes bluer in the outer region. On the other hand, the color of M32 continues to become bluer with the increasing galactocentric distance. We also find, unlike the optical/IR images, significant variations of the position angle and the ellipticity in the ultraviolet isophotes of M31, M81, and NGC 1399 through the inner regions. For M32, the variation is significant in the outer region. Since these variation implies the triaxiality of their intrinsic shapes, we suggest that the early-type galaxies and spiral bulges with a radial color gradient in ultraviolet tend to have a triaxiality. On the other hand, the shape parameter characterized by the fourth order cosine Fourier coefficient of the isophote, a(4)/a, indicates that the systematic deviations of the ultraviolet isophotes of the four galaxies are smaller than ~0.2% in units of the semi-major axis. The latter result implies that the ultraviolet isophotes of the galaxies have a pure elliptical shape rather than the boxy or disky shapes. Therefore, there is no clear evidence of correlation between the radial ultra-violet color gradient and the boxy/disky shapes of isophotes.
        4,000원
        3.
        2000.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We review the early historical developement of astronomical spectrographs, properties of emission line spectra of HII regions in spiral galaxies, and absorption line features of galactic globular clusters. Emission line spectra of HII regions within three spiral galaxies NGC 300, NGC 1365, and NGC 7793, which were observed from AAT/IPCS, had been analysed, and we discuss the abundances of elements in HII regions and the radial abundace gradients through the galaxies. The radial UBV color variations of two globular clusters, NGC 1851 and NGC 2808, were examined for correlations with radial variations of several absorption lines in the integrated spectra, which were obtained from SAAO 74 inch telescope and image tube spectrograph. Nine giant star's spectra in NGC 3201 were also obtained and analysed for the radial abundance gradients in the globular cluster. The results show that the presence of a radial color gradient in a globular cluster is correlated with the presence of abundance gradients. Finally, we suggest some scientific programs for the new high dispersion spectrograph, which will be installed to the BOAO 1.8m telescope.
        4,500원
        4.
        1991.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Using the photographic imagery of the SO galaxy NGC 5102, the equivalent luminosity profile and the fractional integrated luminosity curve have been derived. Several photometric parameters of the galaxy, such as a total magnitude ( B T ), equivalent radius ( r ∗ e ), effective surface brightness ( μ ∗ e ), and concentration indices ( C 21 , C 32 ) were derived from the luminosity profiles. According to the decomposition method from the nonlinear least squares fitting, photometric parameters of the bulge ( μ e , r e ) and the exponential disk ( μ ( 0 ) , α − 1 ), and the bulge to total luminosity ratio (B/T) were obtained. The derived central disk surface brightness ( μ ( 0 ) = 22.06 ± 0.18 m a g / □ " ) and the evaluated B/T ratio (= 0.52) of the NGC 5102 are close to the mean values ( μ ( 0 ) = 21.65 ± 0.3 m a g / □ " , B/T=0.63) of the SO galaxies. Analysis showed that a lens-like hump is embedded in the equivalent luminosity profile of the NGC 5102.
        4,000원