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Journal article
Identification of A-colored stars and structure in the halo of the milky way from Sloan Digital Sky Survey commissioning data
The Astrophysical journal, v 540(2), pp 825-841
10 Sep 2000
Abstract
A sample of 4208 objects with magnitude 15 < g* < 22 and colors of main-sequence A stars have been selected from 370 deg(2) of Sloan Digital Sky Survey (SDSS) commissioning observations. The data is from two long, narrow stripes, each with an opening angle of greater than 60 degrees, at Galactic latitudes 36 degrees < \b\ < 63 degrees on the celestial equator. Relative photometric calibrations good to 2% and consistent absolute photometry allows this uniform sample to be treated statistically over the large area. An examination of the sample's distribution shows that these stars trace considerable substructure in the halo. Large overdensities of A-colored stars in the north at (l, b, R) = (350 degrees, 50 degrees, 46 kpc) and in the south at (157, -58, 33 kpc) and extending over tens of degrees are present in the halo of the Milky Way. Ivezic ct al. have detected the northern structure from a sample of RR Lyrae stars in the SDSS.
Using photometry to separate the stars by surface gravity, both structures are shown to contain a sequence of low surface gravity stars consistent with identification as a blue horizontal branch (BHB). Both structures also contain a population of high surface gravity stars 2 mag fainter than the BHB stars, consistent with their identification as blue stragglers (BSs). The majority of the high surface gravity stars in the Galactic halo may be BS stars like these. A population of F stars associated with the A star excess in the southern structure is detected (the F stars in the northern structure at 46 kpc would be too faint for the SDSS to detect). From the numbers of detected BHB stars, lower limits to the implied mass of the structures are 6 x 10(6) M(circle dot) and 2 x 10(6) M(circle dot), although one does not yet know the full spatial extent of the structures. The fact that two such large clumps have been detected in a survey of only 1% of the sky indicates that such structures are not uncommon in the halo.
Simple spheroidal parameters are fit to a complete sample of the remaining unclumped BHB stars and yield (at r < 40 kpc) a fit to a halo distribution with flattening (c/a = 0.65 +/- 0.2) and a density falloff exponent of alpha = -3.2 +/- 0.3.
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Details
- Title
- Identification of A-colored stars and structure in the halo of the milky way from Sloan Digital Sky Survey commissioning data
- Creators
- B Yanny - FermilabH J Newberg - Rensselaer Polytechnic InstituteS Kent - FermilabS A Laurent-Muehleisen - University of California at Los AngelesPierG T Richards - University of ChicagoC Stoughton - FermilabJ E Anderson - FermilabJ Annis - FermilabJ Brinkmann - New Mexico State UniversityB Chen - Johns Hopkins UniversityCsabaiM Doi - University of TokyoM Fukugita - Institute for Advanced StudyG S Hennessy - United States Naval ObservatoryZ Ivezic - Princeton UniversityG R Knapp - Princeton UniversityR Lupton - Princeton UniversityJ A Munn - United States Department of the NavyT Nash - FermilabC M Rockosi - University of ChicagoD P Schneider - Pennsylvania State UniversityJ A Smith - University of Michigan–Ann ArborD G York - University of Chicago
- Publication Details
- The Astrophysical journal, v 540(2), pp 825-841
- Publisher
- Iop Publishing Ltd
- Number of pages
- 17
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:000089650800019
- Scopus ID
- 2-s2.0-0034633017
- Other Identifier
- 991019201375904721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Astronomy & Astrophysics