A new Milky Way dwarf galaxy in URSA major

Beth Willman; Julianne J. Dalcanton; David Martinez-Delgado; Andrew A. West; Michael R. Blanton; David W. Hogg; J. C. Barentine; Howard J. Brewington; Michael Harvanek; S. J. Kleinman; Jurek Krzesinski; Dan Long; Eric H. Neilsen; Atsuko Nitta; Stephanie A. Snedden

doi:10.1086/431760

A new Milky Way dwarf galaxy in URSA major

Beth Willman, Julianne J. Dalcanton, David Martinez-Delgado, Andrew A. West, Michael R. Blanton, David W. Hogg, J. C. Barentine, Howard J. Brewington, Michael Harvanek, S. J. Kleinman, Jurek Krzesinski, Dan Long, Eric H. Neilsen, Atsuko Nitta, Stephanie A. Snedden

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Abstract

In this Letter, we report the discovery of a new dwarf satellite to the Milky Way, located at (α₂₀₀₀, δ₂₀₀₀) = (158°.72, 51°.92) in the constellation of Ursa Major. This object was detected as an overdensity of red, resolved stars in Sloan Digital Sky Survey data. The color-magnitude diagram of the Ursa Major dwarf looks remarkably similar to that of Sextans, the lowest surface brightness Milky Way companion known, but with approximately an order of magnitude fewer stars. Deeper follow-up imaging confirms that this object has an old and metal-poor stellar population and is ∼100 kpc away. We roughly estimate M_V = -6.75 and r_1/2 = 250 pc for this dwarf. Its luminosity is several times fainter than the faintest known Milky Way dwarf. However, its physical size is typical for dwarf spheroidal galaxies. Even though its absolute magnitude and size are presently quite uncertain, Ursa Major is likely the lowest luminosity and lowest surface brightness galaxy yet known.

Original language	English (US)
Pages (from-to)	L85-L88
Journal	Astrophysical Journal
Volume	626
Issue number	2 II
DOIs	https://doi.org/10.1086/431760
State	Published - Jun 20 2005

Keywords

Galaxies: dwarf
Local Group

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1086/431760

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@article{3168b181ccd445f9936c4ca5694b1891,

title = "A new Milky Way dwarf galaxy in URSA major",

abstract = "In this Letter, we report the discovery of a new dwarf satellite to the Milky Way, located at (α2000, δ2000) = (158°.72, 51°.92) in the constellation of Ursa Major. This object was detected as an overdensity of red, resolved stars in Sloan Digital Sky Survey data. The color-magnitude diagram of the Ursa Major dwarf looks remarkably similar to that of Sextans, the lowest surface brightness Milky Way companion known, but with approximately an order of magnitude fewer stars. Deeper follow-up imaging confirms that this object has an old and metal-poor stellar population and is ∼100 kpc away. We roughly estimate MV = -6.75 and r1/2 = 250 pc for this dwarf. Its luminosity is several times fainter than the faintest known Milky Way dwarf. However, its physical size is typical for dwarf spheroidal galaxies. Even though its absolute magnitude and size are presently quite uncertain, Ursa Major is likely the lowest luminosity and lowest surface brightness galaxy yet known.",

keywords = "Galaxies: dwarf, Local Group",

author = "Beth Willman and Dalcanton, {Julianne J.} and David Martinez-Delgado and West, {Andrew A.} and Blanton, {Michael R.} and Hogg, {David W.} and Barentine, {J. C.} and Brewington, {Howard J.} and Michael Harvanek and Kleinman, {S. J.} and Jurek Krzesinski and Dan Long and Neilsen, {Eric H.} and Atsuko Nitta and Snedden, {Stephanie A.}",

year = "2005",

month = jun,

day = "20",

doi = "10.1086/431760",

language = "English (US)",

volume = "626",

pages = "L85--L88",

journal = "Astrophysical Journal",

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publisher = "American Astronomical Society",

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TY - JOUR

T1 - A new Milky Way dwarf galaxy in URSA major

AU - Willman, Beth

AU - Dalcanton, Julianne J.

AU - Martinez-Delgado, David

AU - West, Andrew A.

AU - Blanton, Michael R.

AU - Hogg, David W.

AU - Barentine, J. C.

AU - Brewington, Howard J.

AU - Harvanek, Michael

AU - Kleinman, S. J.

AU - Krzesinski, Jurek

AU - Long, Dan

AU - Neilsen, Eric H.

AU - Nitta, Atsuko

AU - Snedden, Stephanie A.

PY - 2005/6/20

Y1 - 2005/6/20

N2 - In this Letter, we report the discovery of a new dwarf satellite to the Milky Way, located at (α2000, δ2000) = (158°.72, 51°.92) in the constellation of Ursa Major. This object was detected as an overdensity of red, resolved stars in Sloan Digital Sky Survey data. The color-magnitude diagram of the Ursa Major dwarf looks remarkably similar to that of Sextans, the lowest surface brightness Milky Way companion known, but with approximately an order of magnitude fewer stars. Deeper follow-up imaging confirms that this object has an old and metal-poor stellar population and is ∼100 kpc away. We roughly estimate MV = -6.75 and r1/2 = 250 pc for this dwarf. Its luminosity is several times fainter than the faintest known Milky Way dwarf. However, its physical size is typical for dwarf spheroidal galaxies. Even though its absolute magnitude and size are presently quite uncertain, Ursa Major is likely the lowest luminosity and lowest surface brightness galaxy yet known.

AB - In this Letter, we report the discovery of a new dwarf satellite to the Milky Way, located at (α2000, δ2000) = (158°.72, 51°.92) in the constellation of Ursa Major. This object was detected as an overdensity of red, resolved stars in Sloan Digital Sky Survey data. The color-magnitude diagram of the Ursa Major dwarf looks remarkably similar to that of Sextans, the lowest surface brightness Milky Way companion known, but with approximately an order of magnitude fewer stars. Deeper follow-up imaging confirms that this object has an old and metal-poor stellar population and is ∼100 kpc away. We roughly estimate MV = -6.75 and r1/2 = 250 pc for this dwarf. Its luminosity is several times fainter than the faintest known Milky Way dwarf. However, its physical size is typical for dwarf spheroidal galaxies. Even though its absolute magnitude and size are presently quite uncertain, Ursa Major is likely the lowest luminosity and lowest surface brightness galaxy yet known.

KW - Galaxies: dwarf

KW - Local Group

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JF - Astrophysical Journal

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ER -

A new Milky Way dwarf galaxy in URSA major

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