Deep photometry of Andromeda reveals striking similarities in the tidal stream and spheroid populations

被引:32
作者
Brown, TM
Smith, E
Guhathakurta, P
Rich, RM
Ferguson, HC
Renzini, A
Sweigart, AV
Kimble, RA
机构
[1] Space Telescope Sci Inst, Baltimore, MD 21218 USA
[2] Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA
[3] Univ Calif Los Angeles, Dept Phys & Astron, Div Astron, Los Angeles, CA 90095 USA
[4] Osserv Astron Padova, I-35122 Padua, Italy
[5] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
基金
美国国家科学基金会; 美国国家航空航天局;
关键词
galaxies : evolution; galaxies : halos; galaxies : individual (M31); galaxies : stellar content;
D O I
10.1086/500089
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present a color-magnitude diagram (CMD) for a field in the giant tidal stream of the Andromeda galaxy (M31). These observations, taken with the Advanced Camera for Surveys on the Hubble Space Telescope, are 50% complete at mag, reaching 1 mag below the oldest main-sequence turnoff. Striking similarities V approximate to 30 between the stream and a previous spheroid CMD imply that they have very similar age and metallicity distributions, but present something of an enigma; we speculate on possible interpretations of this result, but we note that none are without problems. Distinct multiple turnoffs, as might be expected from pulses of star formation caused by interaction with Andromeda, are not apparent in the stream CMD. Star formation in both fields lasted about 6 billion years, building up to relatively high metallicities and being largely complete 6 billion years ago. The close similarity of the spheroid and stream suggests that both may have derived from the same event; it would be worth exploring to what extent stars in these structures are the remnants of a disk galaxy that interacted with M31 or even were disrupted from the M31 disk itself by the interaction.
引用
收藏
页码:L89 / L92
页数:4
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