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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



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ID: 559468.0, MPI für Astronomie / Publikationen_mpia
Light curve templates and galactic distribution of RR Lyrae stars from Sloan Digital Sky Survey stripe 82
Authors:Sesar, Branimir; Ivezić, Željko; Grammer, Skyler H.; Morgan, Dylan P.; Becker, Andrew C.; Jurić, Mario;; De Lee, Nathan; Annis, James; Beers, Timothy C.; Fan, Xiaohui; Lupton, Robert H.; Gunn, James E.; Knapp, Gillian R.; Jiang, Linhua; Jester, Sebastian; Johnston, David E.; Lampeitl, Hubert
Language:English
Date of Publication (YYYY-MM-DD):2010
Title of Journal:The Astrophysical Journal
Journal Abbrev.:ApJ
Volume:708
Start Page:717
End Page:741
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:We present an improved analysis of halo substructure traced by RR Lyrae stars in the Sloan Digital Sky Survey (SDSS) stripe 82 region. With the addition of SDSS-II data, a revised selection method based on new ugriz light curve templates results in a sample of 483 RR Lyrae stars that is essentially free of contamination. The main result from our first study persists: the spatial distribution of halo stars at galactocentric distances 5-100 kpc is highly inhomogeneous. At least 20% of halo stars within 30 kpc from the Galactic center can be statistically associated with substructure. We present strong direct evidence, based on both RR Lyrae stars and main-sequence stars, that the halo stellar number density profile significantly steepens beyond a Galactocentric distance of ~30 kpc, and a larger fraction of the stars are associated with substructure. By using a novel method that simultaneously combines data for RR Lyrae and main-sequence stars, and using photometric metallicity estimates for main-sequence stars derived from deep co-added u-band data, we measure the metallicity of the Sagittarius dSph tidal stream (trailing arm) toward R.A. ~2h-3h and decl. ~ 0° to be 0.3 dex higher ([Fe/H] = –1.2) than that of surrounding halo field stars. Together with a similar result for another major halo substructure, the Monoceros stream, these results support theoretical predictions that an early forming, smooth inner halo, is metal-poor compared to high surface brightness material that have been accreted onto a later-forming outer halo. The mean metallicity of stars in the outer halo that are not associated with detectable clumps may still be more metal-poor than the bulk of inner-halo stars, as has been argued from other data sets.
Free Keywords:Galaxy: halo; Galaxy: stellar content; Galaxy: structure; methods: data analysis; stars: horizontal-branch; stars: statistics; stars: variables: other
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/abs/2010ApJ...708..717S [ID No:1]
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