A curious Milky Way satellite in Ursa Major

被引：278

作者：

Zucker, D. B.

Belokurov, V.

Evans, N. W.

Kleyna, J. T.

Irwin, M. J.

Wilkinson, M. I.

Fellhauer, M.

Bramich, D. M.

Gilmore, G.

Newberg, H. J.

Yanny, B.

Smith, J. A.

Hewett, P. C.

Bell, E. F.

Rix, H. -W.

Gnedin, O. Y.

Vidrih, S.

Wyse, R. F. G.

Willman, B.

Grebel, E. K.

Schneider, D. P.

Beers, T. C.

Kniazev, A. Y.

Barentine, J. C.

Brewington, H.

Brinkmann, J.

Harvanek, M.

Kleinman, S. J.

Krzesinski, J.

Long, D.

Nitta, A.

Snedden, S. A.

机构：

[1] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England

[2] Univ Hawaii, Astron Inst, Honolulu, HI 96822 USA

[3] Rensselaer Polytech Inst, Troy, NY 12180 USA

[4] Fermilab Natl Accelerator Lab, Batavia, IL 60510 USA

[5] Los Alamos Natl Lab, ISR4, Los Alamos, NM 87545 USA

[6] Austin Peay State Univ, Dept Phys & Astron, Clarksville, TN 37044 USA

[7] Max Planck Inst Astron, D-69117 Heidelberg, Germany

[8] Ohio State Univ, Dept Phys, Columbus, OH 43210 USA

[9] Johns Hopkins Univ, Baltimore, MD 21218 USA

[10] NYU, Ctr Cosmol & Particle Phys, Dept Phys, New York, NY 10003 USA

[11] Univ Basel, Inst Astron, Dept Phys, CH-4102 Binningen, Switzerland

[12] Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA

[13] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA

[14] S African Astron Observ, ZA-7935 Cape Town, South Africa

[15] Apache Point Observ, Sunspot, NM 88349 USA

[16] Subaru Telescope, Hilo, HI 96720 USA

[17] Cracow Pedagog Univ, Mt Suhora Observ, PL-30084 Krakow, Poland

[18] Gemini Observ, Hilo, HI 96720 USA

来源：

ASTROPHYSICAL JOURNAL | 2006年 / 650卷 / 01期

基金：

美国国家科学基金会; 美国国家航空航天局;

关键词：

galaxies : dwarf; galaxies : individual (Ursa Major II); local group;

D O I：

10.1086/508628

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

In this Letter, we study a localized stellar overdensity in the constellation of Ursa Major, first identified in Sloan Digital Sky Survey (SDSS) data and subsequently followed up with Subaru imaging. Its color-magnitude diagram (CMD) shows a well-defined subgiant branch, main sequence, and turnoff, from which we estimate a distance of similar to 30 kpc and a projected size of similar to 250 x 125 pc(2). The CMD suggests a composite population with some range in metallicity and/or age. Based on its extent and stellar population, we argue that this is a previously unknown satellite galaxy of the Milky Way, hereby named Ursa Major II (UMa II) after its constellation. Using SDSS data, we find an absolute magnitude of, which would make it the faintest known satellite galaxy. UMa II's isophotes are irregular M-V similar to -3.8 and distorted with evidence for multiple concentrations; this suggests that the satellite is in the process of disruption.

引用

页码：L41 / L44

页数：4

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