A New Milky Way Dwarf Galaxy in Ursa Major | Zendy

Beth Willman | Zendy; Julianne J. Dalcanton | Zendy; David MartínezDelgado | Zendy; Andrew A. West | Zendy; Michael R. Blanton | Zendy; David W. Hogg | Zendy; John C. Barentine | Zendy; H. Brewington | Zendy; Michael Harvanek | Zendy; S. J. Kleinman | Zendy; J. Krzesiński | Zendy; Dan Long | Zendy; Eric H. Neilsen | Zendy; A. Nitta | Zendy; Stephanie A. Snedden | Zendy

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A New Milky Way Dwarf Galaxy in Ursa Major

Author(s) -

Beth Willman,

Julianne J. Dalcanton,

David MartínezDelgado,

Andrew A. West,

Michael R. Blanton,

David W. Hogg,

John C. Barentine,

H. Brewington,

Michael Harvanek,

S. J. Kleinman,

J. Krzesiński,

Dan Long,

Eric H. Neilsen,

A. Nitta,

Stephanie A. Snedden

Publication year - 2005

Publication title -

the astrophysical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.376

H-Index - 489

eISSN - 1538-4357

pISSN - 0004-637X

DOI - 10.1086/431760

Subject(s) - milky way , physics , dwarf galaxy , astrophysics , dwarf spheroidal galaxy , absolute magnitude , astronomy , local group , surface brightness , galaxy , stellar population , luminosity , dwarf galaxy problem , magnitude (astronomy) , star formation , interacting galaxy

In this Letter, we report the discovery of a new dwarf satellite to the MilkyWay, located at ($\alpha_{2000}, \delta_{2000}$) $=$ (158.72,51.92) in theconstellation of Ursa Major. This object was detected as an overdensity of red,resolved stars in Sloan Digital Sky Survey data. The color-magnitude diagram ofthe Ursa Major dwarf looks remarkably similar to that of Sextans, the lowestsurface brightness Milky Way companion known, but with approximately an orderof magnitude fewer stars. Deeper follow-up imaging confirms this object has anold and metal-poor stellar population and is $\sim$ 100 kpc away. We roughlyestimate M$_V =$ -6.75 and $r_{1/2} =$ 250 pc for this dwarf. Its luminosity isseveral times fainter than the faintest known Milky Way dwarf. However, itsphysical size is typical for dSphs. Even though its absolute magnitude and sizeare presently quite uncertain, Ursa Major is likely the lowest luminosity andlowest surface brightness galaxy yet known.Comment: Replaced with ApJL accepted version. Includes some additional details, corrected references, and minor changes to Figure

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