Identification of A-colored Stars and Structure in the Halo of the Milky Way from Sloan Digital Sky Survey Commissioning Data

By Brian Yanny, Heidi Jo Newberg, S. Kent, S. Laurent-Muehleisen, J. Pier, Gordon Richards, C. Stoughton, J. Anderson, James Annis, J. Brinkmann and 14 more. 2000

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A sample of 4208 objects with magnitude 15 < g* < 22 and colors of main-sequence A stars have been selected from 370 deg2 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°, at Galactic latitudes 36° < |b| < 63° 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°, 50°, 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 et 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 × 106 M☉ and 2 × 106 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.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

The Milky Way Tomography with SDSS. I. Stellar Number Density Distribution (2005, background): “Examples include the Sgr dwarf tidal stream in the halo (Ivezić et al. 2000; Yanny et al. 2000; Vivas et al. 2001; Majewski et al. 2003) or the Monoceros stream closer to the Galactic plane (Newberg et al. 2002; Rocha-Pinto et al. 2003).”
How Lumpy Is the Milky Way’s Dark Matter Halo? (2001, background): “However several deep-halo surveys are currently underway that have the potential of tracing these streams out further (Ivezić et al. 2000; Yanny et al. 2000; Majewski et al. 2000a; Morrison et al. 2000).”
Tracing Galaxy Formation with Stellar Halos. I. Methods (2005, background): “…for the size, shape and extent of the Milky Way’s stellar halo come either from star count surveys (Morrison et al. 2000; Chiba & Beers 2000; Yanny et al. 2000; Siegel, Majewski, Reid, & Thompson 2002) or studies where distances could be estimated using RR Lyraes (Wetterer & McGraw 1996;…”
The stellar halo of the Galaxy (2008, methodology): “Typically RR Lyrae and blue horizontal branch stars (BHB) were used as tracers.”
CHEMICAL EVOLUTION IN HIERARCHICAL MODELS OF COSMIC STRUCTURE. II. THE FORMATION OF THE MILKY WAY STELLAR HALO AND THE DISTRIBUTION OF THE OLDEST STARS (2009, background): “As examples of the former, there is now a proliferating number of known stellar streams (Yanny et al. 2000) and faint dwarf galaxies (Belokurov et al. 2007) discovered in the Sloan Digital Sky Survey.”
Substructure revealed by RR Lyraes in SDSS Stripe 82 (2009, background): “A final view of Stripe 82 is provided in Figure 18, which shows the density distribution of blue horizontal branch stars (BHBs) and blue stragglers (BSs), selected using the colourcuts of Yanny et al. (2000).”
Evidence for Stellar Substructure in the Halo and Outer Disk of M31 (2002, background): “…dwarf galaxy and associated stellar streams (e.g., Ibata, Gilmore, & Irwin 1995; Mateo, Olszewski, & Morrison 1998; Majewski et al. 1999; Yanny et al. 2000; Ibata et al. 2001b; Ibata et al. 2001c), the phase-space clumping of halo stars in the solar neighborhood (Helmi et al. 1999), and…”
Detection of Massive Tidal Tails around the Globular Cluster Palomar 5 with Sloan Digital Sky Survey Commissioning Data (2000, background): “Such a high-quality database is ideally suited for studies of Galactic structure (e.g., Yanny et al. 2000; Ivezic et al. 2000) and lends itself in particular to searches for tidal debris with unprecedented depth and spatial coverage.”
Precession of the Sagittarius stream (2013, methodology): “At high Galacticlatitudes, the principal source of false positives within the boundaries of the colour-colour box proposed by Yanny et al. (2000) are the intrinsically less luminous Blue Straggler (BS) stars.”
The Accretion Origin of the Milky Way’s Stellar Halo (2007, background): “…alpha element enhancement, a high degree of support from random motions, and a roughlyr−3 power law distribution in an oblate halo (Eggen, Lynden-Bell & Sandage 1962; Chiba & Beers 2000; Yanny et al. 2000; Larsen & Humphreys 2003; Lemon et al. 2004; Newberg & Yanny 2005; Jurić et al. 2007).”
Galactic Halo Substructure in the Sloan Digital Sky Survey: The Ancient Tidal Stream from the Sagittarius Dwarf Galaxy (2000, background): “These include, among others, the “spaghetti” survey (Morrison et al. 2000), the APM carbon star survey (Totten & Irwin 1998; Totten, Irwin, & Whitelock 2000; Ibata et al. 2001, hereafter Paper I), and the Sloan Digital Sky Survey (SDSS; Yanny et al. 2000; Ivezić et al. 2000).”
The Milky Way’s Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from the Kinematics of ~2400 SDSS Blue Horizontal-Branch Stars (2008, methodology): “We start our selection of BHB stars by adopting the color cuts for identification of BHB candidates used in Yanny et al. (2000): 0.8 < u − g < 1.6 −0.5 < g − r < 0.0 These color cuts are shown in Figure 1; the rectangle is the region of BHB candidates.”
Stellar Abundance and Galactic Chemical Evolution through LAMOST Spectroscopic Survey (2006, background): “It would be very interesting to make in situ studies of abundances and kinematics of stars in the various places of the thin and thick disks, such as the low-resolution spectroscopic survey of the stars situated at 0.5–5kpc from the Galactic plane (Gilmore et al. 2002) and the spectroscopic study ba”
Great Circle Tidal Streams: Evidence for a Nearly Spherical Massive Dark Halo around the Milky Way (2000, background): “…much more numerous fainter stars spatially and kinematically associated with the C stars presented above.7 7 After the submission of this article, Yanny et al. (2000) and et al.Ivezic (2000) discovered the presence of a large population of A-colored halo stars in the SDSS data set, distributed…”
Cosmological simulations of the formation of the stellar haloes around disc galaxies (2011, methodology): “…that were used (Harris 1976; Zinn 1985; Saha 1985; Preston, Shectman Beers 1991; Wetterer & McGraw 1996; Ivezić et al. 2000; Morrison et al. 2000; Yanny et al. 2000; Chiba & Beers 2000; Chen et al. 2001; Siegel et al. 2002; Vivas & Zinn 2006; Bell et al. 2008; Juŕıc et al. 2008; Smith et al.…”
The Milky Way Tomography with SDSS. II. Stellar Metallicity (2008, background): “However, recent discoveries of complex substructure in the distribution and kinematics of the Milky Way’s stars (e.g. Ivezić et al. 2000; Yanny et al. 2000; Vivas et al. 2001; Newberg et al. 2002; Gilmore, Wyse & Norris 2002; Majewski et al. 2003; Duffau, Zinn & Vivas 2006; Vivas & Zinn 2006;…”
The radial velocity dispersion profile of the Galactic halo : constraining the density profile of the dark halo of the Milky Way (2005, methodology): “The latter has been determined to vary as a power-law ρ∗(r) ∝ r −γ with γ ∼ 3.5 out to ∼ 50 kpc (Morrison et al. 2000; Yanny et al. 2000), and we shall assume this behaviour can be extrapolated all the way out to our last measured point.”
The QUEST RR Lyrae Survey. II. The Halo Overdensities in the First Catalog (2006, background): “This striking overdensity was discovered in the spatial distribution of A stars (Yanny et al. 2000) and RRLS candidates (Ivezić et al. 2000).”