NOAO >   Observing Info >   Approved Programs >   2011B-0230

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Proposal Information for 2011B-0230


PI: Matthew G. Walker, Harvard University, mwalker@cfa.harvard.edu
Address: Center for Astrophysics, 60 Garden St., MS-51, Cambridge, MA 02138, United States

CoI: Alis Deason, IoA, University of Cambridge UK
CoI: Vasily Belokurov, IoA, University of Cambridge UK

Title: Distant Tracers of the Milky Way Halo

Abstract: Due to the rarity of tracers at large distances, the outermost reaches of our Galaxy (D > 100 kpc) are largely unexplored. Modern cosmological models invoke dark matter halos that can extend out to 200- 300 kpc but current observations constrain the Milky Way's mass only within ~ 50 kpc. Blue horizontal branch stars (BHBs) are old, metal-poor and intrinsically bright, and can therefore provide a convenient probe of the Galaxy's stellar halo. We have used stacked photometry in SDSS Stripe 82, as well as overlap regions in SDSS DR8, to identify 40 possible BHB candidates out to distances of 200 kpc. Photometric classification of these stars is difficult at faint magnitudes owing to the poor SDSS u-band photometry. We request one night with the optical imager at SOAR to obtain deep and accurate u-band photometry of these targets in order to confirm their status as the most distant available tracers of the Milky Way halo.


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NOAO >   Observing Info >   Approved Programs >   2011B-0230

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