LIGHT CURVE TEMPLATES AND GALACTIC DISTRIBUTION OF RR LYRAE STARS FROM SLOAN DIGITAL SKY SURVEY STRIPE 82

By B. Sesar, Željko Ivezic´, S. Grammer, D. Morgan, A. Becker, Mario Juric, Nathan De Lee, James Annis, Timothy C. Beers, Xiaohui Fan and 7 more. 2009

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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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/4da6e3236c0bd77be893b189ed101d319f2f863f

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Citations in the corpus

MAPPING THE STELLAR STRUCTURE OF THE MILKY WAY THICK DISK AND HALO USING SEGUE PHOTOMETRY (2009, background): “Halo parameters, when described by a single powerlaw, are probably varying with radius (e.g. Bell et al. 2008; Watkins et al. 2009; Sesar et al. 2010), and in this study only the stellar halo within a radius of 25 kpc from the Sun has been considered.”
THE SLOAN DIGITAL SKY SURVEY COADD: 275 deg2 OF DEEP SLOAN DIGITAL SKY SURVEY IMAGING ON STRIPE 82 (2011, background): “For a detailed study of the Milky Way structure in Stripe 82, see, e.g., Sesar et al. (2010).”
Understanding the Lomb–Scargle Periodogram (2017, methodology): “Another approach is to use empirically-derived templates as a functional fit at each frequency; this has been employed effectively in Sesar et al. (2010, 2013) and related work.”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “…al. (2011) BHB, BS 10–45 2.3 ± 0.1 0.59 ± 0.03 27.1 ± 1 4.6 ± 0.15 Faccioli et al. (2014) RRL 9–49 2.8 ± 0.4 0.7 fixed 28.5 ± 5.6 4.4 ± 0.7 Sesar et al. (2013) RRL 5–30 1–2.7 0.63 ± 0.05 16 ± 1 2.7 ± 0.3 Sesar et al. (2010) RRL 9–49 2.8 ± 0.2 0.7 fixed 34.6 ± 2.8 5.8 ± 0.9 Watkins et al. (2009)…”
THE CASE FOR THE DUAL HALO OF THE MILKY WAY (2011, background): “Both Watkins et al. (2009) and Sesar et al. (2010) have argued persuasively that single power-law profiles are incapable of describing the spatial variation of the halo system.”
The Milky Way stellar halo out to 40 kpc: squashed, broken but smooth (2011, result): “Our broken powerlaw model is in very good agreement agreement with the results of Watkins et al. (2009), who use a sample of RR Lyrae stars to probe the density distribution of the stellar halo out to∼ 100 kpc (see also Sesar et al. 2010).”
LSST: From Science Drivers to Reference Design and Anticipated Data Products (2008, background): “The LSST in its standard surveying mode will be able to detect RR Lyrae variables (pulsating stars and standard candles) and classical novae (exploding stars and standard candles) at a distance of 400 kpc and hence explore the extent and structure of our halo out to half the distance to the Andromed”