A low-latitude halo stream around the Milky Way

被引:347
作者
Yanny, B
Newberg, HJ
Grebel, EK
Kent, S
Odenkirchen, M
Rockosi, CM
Schlegel, D
Subbarao, M
Brinkmann, J
Fukugita, M
Ivezic, Z
Lamb, DQ
Schneider, DP
York, DG
机构
[1] Fermilab Natl Accelerator Lab, Batavia, IL 60510 USA
[2] Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA
[3] Max Planck Inst Astron, D-69117 Heidelberg, Germany
[4] Univ Washington, Seattle, WA 98195 USA
[5] Princeton Univ, Princeton, NJ 08544 USA
[6] Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA
[7] Apache Point Observ, Sunspot, NM 88349 USA
[8] Univ Tokyo, Inst Cosm Ray Res, Tokyo, Japan
[9] Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA
关键词
Galaxy : halo; Galaxy : structure;
D O I
10.1086/374220
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present evidence for a ring of stars in the plane of the Milky Way, extending at least from l=180degrees to 227degrees with turnoff magnitude gsimilar to19.5; the ring could encircle the Galaxy. We infer that the low Galactic latitude structure is at a fairly constant distance of R=18+/-2 kpc from the Galactic center above the Galactic plane and has R=20+/-2 kpc in the region sampled below the Galactic plane. The evidence includes 500 Sloan Digital Sky Survey spectroscopic radial velocities of stars within 30degrees of the plane. The velocity dispersion of the stars associated with this structure is found to be 27 km s(-1) at (l,b)=(198degrees, -27degrees), 22 km s(-1) at (l,b)=(225degrees, 28degrees), 30 km s(-1) at (l,b)=(188degrees, 24degrees), and 30 km s(-1) at (l,b)=(182degrees, 27degrees). The structure rotates in the same prograde direction as the Galactic disk stars but with a circular velocity of 110+/-25 km s(-1). The narrow measured velocity dispersion is inconsistent with power-law spheroid or thick-disk populations. We compare the velocity dispersion in this structure with the velocity dispersion of stars in the Sagittarius dwarf galaxy tidal stream, for which we measure a velocity dispersion of 20 km s(-1) at (l,b)=(165degrees, -55degrees). We estimate a preliminary metallicity from the Ca II (K) line and color of the turnoff stars of [Fe/H]= -1.6 with a dispersion of 0.3 dex and note that the turnoff color is consistent with that of the spheroid population. We interpret our measurements as evidence for a tidally disrupted satellite of 2x10(7) to 5x10(8) M-circle dot that rings the Galaxy.
引用
收藏
页码:824 / 841
页数:18
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