Stellar kinematics in the remote Leo II dwarf spheroidal galaxy-another brick in the wall

被引:104
|
作者
Koch, Andreas [1 ]
Kleyna, Jan T.
Wilkinson, Mark I.
Grebel, Eva K.
Gilmore, Gerard F.
Evans, N. Wyn
Wyse, Rosemary F. G.
Harbeck, Daniel R.
机构
[1] Univ Basel, Astron Inst, Dept Phys & Astron, Binningen, Switzerland
[2] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90024 USA
[3] Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA
[4] Univ Cambridge, Inst Astron, Cambridge CB2 1TN, England
[5] Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England
[6] Heidelberg Univ, Astron Rechen Inst, Zentrum Astron Heidelberg, D-6900 Heidelberg, Germany
[7] Johns Hopkins Univ, Baltimore, MD 21218 USA
[8] Univ Wisconsin, Dept Astron, Madison, WI 53706 USA
来源
ASTRONOMICAL JOURNAL | 2007年 / 134卷 / 02期
基金
英国科学技术设施理事会;
关键词
galaxies : dwarf; galaxies : individual (Leo II); galaxies : kinematics and dynamics; galaxies : stellar content; galaxies : structure; Local Group;
D O I
10.1086/519380
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present the projected velocity dispersion profile for the remote (d = 233 kpc) Galactic dwarf spheroidal (dSph) galaxy Leo II, based on 171 discrete stellar radial velocities that were obtained from medium-resolution spectroscopy using the FLAMES/GIRAFFE spectrograph at the European Southern Observatory, Chile. The dispersion profile of those stars with good membership probabilities is essentially flat, with an amplitude of 6.6 +/- 0.7 km s(-1) over the full radial extent of our data, which probe to the stellar boundary of this galaxy. We find no evidence of any significant apparent rotation or velocity asymmetry, which suggests that tidal effects cannot be invoked to explain Leo Il's properties. From basic mass modeling, employing the Jeans equation, we derive a mass out to the limiting radius of (2.7 +/- 0.5) x 10(7) M-circle dot and a global mass-to-light ratio of 27-45 in solar units, depending on the adopted total luminosity. A cored halo profile and a mild amount of tangential velocity anisotropy is found to account well for Leo II's observed kinematics, although we cannot exclude the possibility of a cusped halo with radially varying velocity anisotropy. All in all, this galaxy exhibits dark matter properties that appear to be concordant with the other dSph satellites of the Milky Way, namely, a halo mass profile that is consistent with a central core and a total mass that is similar to the common mass scale seen in other dSphs.
引用
收藏
页码:566 / 578
页数:13
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