Stellar populations in the dwarf elliptical galaxy NGC 147

被引:85
作者
Han, M
Hoessel, JG
Gallagher, JS
Holtzman, J
Stetson, PB
Trauger, J
Ballester, GE
Burrows, C
Clarke, J
Crisp, D
Griffiths, R
Grillmair, C
Hester, J
Krist, J
Mould, JR
Scowen, P
Stapelfeldt, K
Watson, A
Westphal, J
机构
[1] NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003
[2] DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA
[3] CALTECH,JET PROP LAB,PASADENA,CA 91109
[4] UNIV MICHIGAN,DEPT ATMOSPHER & OCEAN SCI,ANN ARBOR,MI 48109
[5] SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218
[6] ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287
[7] AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA
[8] CALTECH,PASADENA,CA 91125
关键词
D O I
10.1086/118316
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Deep V and I CCD images in a central and an outer field of the Local Group dwarf elliptical galaxy NGC 147 have been obtained with the Wide Field and Planetary Camera-2 (WFPC2) on board of the Hubble Space Telescope. The color-magnitude diagram shows a number of interesting features, including a well defined red giant branch (RGB); a red horizontal branch (HB), a strong red clump, and a small number of extended asymptotic giant branch (EAGB) stars. A mean distance modulus of (m-M)(0)=24.39 is derived based on both the HB and the RGB tip brightness. The metallicity [Fe/H] as determined from the RGB color has a mean value of -0.91 in the central field, and -1.0 in the outer field; and the outer field shows a weak tendency of increasing metallicity with galactocentric radius. A metallicity dispersion is also present in the galaxy, and it shows a clear radial variation in the sense that a larger dispersion is seen at smaller radii. The small population of EAGB stars indicates the presence of intermediate-aged (several Gyr) stars in the galaxy, while the absence of the main sequence stars with M(V)<1 shows that star formation ceased at least 1 Gyr ago. The distribution of the EAGB stars indicates that the younger stars are more centrally concentrated than the majority of older stars. A similar age gradient is also implied by the relative distribution of the HB stars, which appear to be more populous at larger radii. These results are considered within the context of theoretical models for the evolution of dwarf elliptical galaxies. (C) 1997 American Astronomical Society.
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页码:1001 / &
页数:12
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