A New Milky Way Dwarf Galaxy in Ursa Major

By B. Willman, J. J. Dalcanton, D. Martínez-Delgado, Andrew A. West, M. Blanton, David W. Hogg, John C. Barentine, H. Brewington, M. Harvanek, S. Kleinman and 5 more. 2005

402 citations recorded by the source corpus.

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.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/d766a98fa2255233e543ef6417012728faa72f24

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

Citations in the corpus

CLUMPY STREAMS FROM CLUMPY HALOS: DETECTING MISSING SATELLITES WITH COLD STELLAR STRUCTURES (2010, background): “Recent, large-area stellar surveys have discovered dozens of new satellite galaxies, most notably using the Sloan Digital Sky Survey (SDSS, e.g. Willman et al. 2005; Belokurov et al. 2006a, 2007; Zucker et al. 2006; Irwin et al. 2007; Koposov et al. 2007; Walsh et al. 2007) but the number…”
EIGHT NEW MILKY WAY COMPANIONS DISCOVERED IN FIRST-YEAR DARK ENERGY SURVEY DATA (2015, background): “Over the past decade, systematic searches of wide-field SDSS imaging have revealed 15 additional arcminute-scale, resolved stellar overdensities (Willman et al. 2005a, 2005b; Belokurov et al. 2006, 2007, 2008, 2009, 2010; Grillmair 2006, 2009; Sakamoto & Hasegawa 2006; Zucker et al. 2006a, 2006b;…”
Galaxy and Mass Assembly (GAMA): survey diagnostics and core data release (2010, background): “…types (e.g. Kirkpatrick et al. 1999), tidal streams in the Galactic halo (e.g. Belokurov et al. 2006), new populations of dwarf galaxies (e.g. Willman et al. 2005), galaxy population statistics (e.g. Bell et al. 2003; Baldry et al. 2006), the recent cosmic star formation history (e.g.…”
Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1 (2019, methodology): “…multi-band optical imaging surveys— combined with automated search algorithms—have greatly increased the known population of Milky Way satellites (Willman et al. 2005a,b; Zucker et al. 2006a,b; Belokurov et al. 2006, 2007, 2008, 2009, 2010; Grillmair 2006, 2009; Sakamoto & Hasegawa 2006; Irwin…”
DWARF GALAXY ANNIHILATION AND DECAY EMISSION PROFILES FOR DARK MATTER EXPERIMENTS (2014, methodology): “…S. M., Jerjen, H., & Willman, B. 2007, ApJ, 662, L83 Wechsler, R. H., Zentner, A. R., Bullock, J. S., Kravtsov, A. V., & Allgood, B. 2006, ApJ, 652, 71 Willman, B., Geha, M., Strader, J., et al. 2011, AJ, 142, 128 Willman et al. 2005, ApJ, 626, L85 Zentner, A. R., & Bullock, J. S. 2002, Phys.”
The properties of warm dark matter haloes (2013, background): “A number of new dwarf spheroidal (dSph) satellite galaxies have been discovered around the Milky Way and M31 (e.g. Willman et al. 2005; Walsh et al. 2007; Martin et al. 2009; Bell et al. 2011; Martin et al. 2013).”
Galactic Searches for Dark Matter (2012, background): “overdensities of stars through imaging data. As of the publication of this article, searches of the SDSS data for overdensities of stars in color space have revealed a dozen new Milky Way satellites (Willman et al., 2005; Belokurov et al., 2007b). The distances to these objects are determined by com”
BIG FISH, LITTLE FISH: TWO NEW ULTRA-FAINT SATELLITES OF THE MILKY WAY (2010, background): “Ultra-faint satellites of the Milky Way include dwarf galaxies (Willman et al. 2005; Zucker et al. 2006a,b; Belokurov et al. 2006, 2007a; Irwin et al. 2007; Belokurov et al. 2008) and star clusters (Koposov et al. 2007), as well as objects with intermediate properties (Walsh et al. 2007; Belokurov…”
THE INVISIBLES: A DETECTION ALGORITHM TO TRACE THE FAINTEST MILKY WAY SATELLITES (2008, methodology): “Twelve of these would be the known objects Boötes, Draco, Canes Venatici I and II, Coma Berenices, Leo I, Leo II, Leo IV, Leo V, Hercules, Ursa Major, and Ursa Major II, leaving one (12) possible missing satellite(s).”
One Law to Rule Them All: The Radial Acceleration Relation of Galaxies (2016, background): “Ultrafaint dSphs have been discovered during the past ∼10 years with the advent of the Sloan Digital Sky Survey (e.g., Willman et al. 2005) and Dark Energy Survey (e.g., Koposov et al. 2015a).”
Tracing Galaxy Formation with Stellar Halos. I. Methods (2005, background): “…given the luminosity and surface brightness limits of prior searches (as the recent discovery of the Ursa Minor dwarf spheroidal demonstrates, see Willman et al. 2005), but incompleteness is not seen as a viable solution for a problem of this scale (see Willman et al. 2004, for a discussion).”
The Baryon Content of Extremely Low Mass Dwarf Galaxies (2006, background): “By far the best known set of dwarfs is that in the Local Group (Mateo 1998; Grebel et al. 2003; Dolphin et al. 2005), where the even the lowest mass dwarfs can be detected as over-densities in stellar counts (Willman et al. 2005; Zucker et al. 2004).”
UPDATED NEARBY GALAXY CATALOG (2013, background): “This volume contains dwarf galaxies with luminosities 104 times lower than that of the Milky Way, and it includes more than a dozen groups, similar to our Local Group in size and population.”
The AIMSS Project I: bridging the star cluster, galaxy divide (2014, background): “…et al. 2005, 2011a; Brodie et al. 2011; Forbes et al. 2013), additional Milky Way (MW) and M31 dwarf spheroidals and ultrafaint dwarf galaxies (e.g. Willman et al. 2005; Zucker et al. 2006, 2007; Belokurov et al. 2007), and a host of new cEs (Mieske et al. 2005; Chilingarian et al. 2007; Smith…”
Luminosity function and radial distribution of Milky Way satellites in a ΛCDM Universe (2009, background): “As a result the number of known dwarf spheroidals has doubled in the recent past (e.g Willman et al. 2005, Zucker et al. 2006; Belokurov et al. 2007; Irwin et al. 2007, Gilmore et al. 2007).”
THE LEAST-LUMINOUS GALAXY: SPECTROSCOPY OF THE MILKY WAY SATELLITE SEGUE 1 (2008, background): “…magnitudes fainter than MV = −8, have all been found in the Sloan Digital Sky Survey (SDSS) via slight statistical over-densities of individual stars (Willman et al. 2005a,b; Zucker et al. 2006a,b; Belokurov et al. 2006a, 2007; Sakamoto & Hasegawa 2006; Irwin et al. 2007; Walsh et al. 2007).”