Strangers in the night:: Discovery of a dwarf spheroidal galaxy on its first local group infall

被引:47
作者
Chapman, S. C.
Penarrubia, J.
Ibata, R.
McConnachie, A.
Martin, N.
Irwin, M.
Blain, A.
Lewis, G. F.
Letarte, B.
Lo, K.
Ludlow, A.
O'Neil, K.
机构
[1] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
[2] Univ Victoria, Victoria, BC V8P 1A1, Canada
[3] CALTECH, Pasadena, CA 91125 USA
[4] Observ Starsbourg, F-67000 Strasbourg, France
[5] Max Planck Inst Astron, D-69117 Heidelberg, Germany
[6] Univ Sydney, Sch Phys, Inst Astron, Sydney, NSW 2006, Australia
[7] NRAO, Green Bank, WV 24944 USA
基金
英国科学技术设施理事会;
关键词
galaxies : evolution; galaxies : individual (Andromeda); galaxies : spiral; Local Group;
D O I
10.1086/519377
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present spectroscopic observations of the And XII dwarf spheroidal galaxy using DEIMOS/Keck II, showing it to be moving rapidly through the Local Group (-556 km s(-1) heliocentric velocity, -281 km s(-1) relative to Andromeda), falling into the Local Group from similar to 115 kpc beyond Andromeda's nucleus. And XII therefore represents a dwarf galaxy plausibly falling into the Local Group for the first time and never having experienced a dense galactic environment. From Green Bank Telescope observations, a limit on the H I gas mass of <3 x 103 M-circle dot suggests that And XII's gas gas could have been removed prior to experiencing the tides of the Local Group galaxies. Orbit models suggest that the dwarf is close to the escape velocity of M31 for published mass models. And XII is our best direct evidence for the late infall of satellite galaxies, a prediction of cosmological simulations.
引用
收藏
页码:L79 / L82
页数:4
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