THE STELLAR METALLICITY DISTRIBUTION FUNCTION OF THE GALACTIC HALO FROM SDSS PHOTOMETRY

Journal Article · Sun Jan 20 04:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/763/1/65· OSTI ID:22167189

An, Deokkeun ^[1]; Beers, Timothy C. ^[2]; Johnson, Jennifer A.; Pinsonneault, Marc H. ^[3]; Lee, Young Sun ^[4]; Bovy, Jo ^[5]; Ivezic, Zeljko ^[6]; Carollo, Daniela ^[7]; Newby, Matthew ^[8]

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1. Department of Science Education, Ewha Womans University, Seoul 120-750 (Korea, Republic of)
2. National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)
3. Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
4. Department of Physics and Astronomy and JINA (Joint Institute for Nuclear Astrophysics), Michigan State University, E. Lansing, MI 48824 (United States)
5. Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)
6. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
7. Macquarie University Research Centre in Astronomy, Astrophysics and Astrophotonics, Department of Physics and Astronomy, Macquarie University, NSW 2109 (Australia)
8. Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute Troy, NY 12180 (United States)

We explore the stellar metallicity distribution function of the Galactic halo based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using observations of several star clusters and validated by comparisons with medium-resolution spectroscopic values over a wide range of metal abundance. We estimate distances and metallicities for individual main-sequence stars in the multiply scanned SDSS Stripe 82, at heliocentric distances in the range 5-8 kpc and |b| > 35 Degree-Sign , and find that the in situ photometric metallicity distribution has a shape that matches that of the kinematically selected local halo stars from Ryan and Norris. We also examine independent kinematic information from proper-motion measurements for high Galactic latitude stars in our sample. We find that stars with retrograde rotation in the rest frame of the Galaxy are generally more metal poor than those exhibiting prograde rotation, which is consistent with earlier arguments by Carollo et al. that the halo system comprises at least two spatially overlapping components with differing metallicity, kinematics, and spatial distributions. The observed photometric metallicity distribution and that of Ryan and Norris can be described by a simple chemical evolution model by Hartwick (or by a single Gaussian distribution); however, the suggestive metallicity-kinematic correlation contradicts the basic assumption in this model that the Milky Way halo consists primarily of a single stellar population. When the observed metallicity distribution is deconvolved using two Gaussian components with peaks at [Fe/H] Almost-Equal-To -1.7 and -2.3, the metal-poor component accounts for {approx}20%-35% of the entire halo population in this distance range.

• OSTI ID: 22167189
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 763; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
COMPARATIVE EVALUATIONS
CORRELATIONS
DISTRIBUTION FUNCTIONS
ELEMENT ABUNDANCE
GALACTIC EVOLUTION
GAUSS FUNCTION
HYDROGEN
IRON
MAIN SEQUENCE STARS
MILKY WAY
PHOTOMETRY
PROPER MOTION
RESOLUTION
ROTATION
SPATIAL DISTRIBUTION
STAR CLUSTERS
STAR EVOLUTION