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2000ApJ...540..825Y - Astrophys. J., 540, 825-841 (2000/September-2)
Identification of A-colored stars and structure in the halo of the Milky Way from Sloan Digital Sky Survey commissioning data.
YANNY B., NEWBERG H.J., KENT S., LAURENT-MUEHLEISEN S.A., PIER J.R., RICHARDS G.T., STOUGHTON C., ANDERSON J.E.Jr, ANNIS J., BRINKMANN J., CHEN B., CSABAI I., DOI M., FUKUGITA M., HENNESSY G.S., IVEZIC Z., KNAPP G.R., LUPTON R., MUNN J.A., NASH T., ROCKOSI C.M., SCHNEIDER D.P., SMITH J.A. and YORK D.G.
Abstract (from CDS):
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 6x106 M☉ and 2x106 M☉, 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 α=-3.2±0.3.
Abstract Copyright: ∼
Journal keyword(s): Stars: Blue Stragglers - Galaxy: Halo - Galaxy: Structure - Stars: Early-Type - Stars: Horizontal-Branch
CDS comments: The two concentrations of stars are studied in 2002ApJ...569..245N and designated as [NYR2002] S341+57-22.5 and [NYR2002] S167-54-21.5 in SIMBAD.
Simbad objects: 16
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