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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 308510.0, MPI für Astronomie / Publikationen_mpia
A curious Milky Way satellite in Ursa Major
Authors: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.
Date of Publication (YYYY-MM-DD):2006
Journal Abbrev.:The Astrophysical Journal
Start Page:L41
End Page:L44
Audience:Not Specified
Abstract / Description: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 ~30 kpc and a projected size of ~250×125 pc2. 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 MV~-3.8, which would make it the faintest known satellite galaxy. UMa II's isophotes are irregular and distorted with evidence for multiple concentrations; this suggests that the satellite is in the process of disruption. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.
Free Keywords:Galaxies: Dwarf; galaxies: individual (Ursa Major II); Galaxies: Local Group
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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