NOAO >   Observing Info >   Approved Programs >   2012B-0540

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Proposal Information for 2012B-0540


PI: Puragra Guhathakurta, UCO/Lick Obs., Univ. of Calif. Santa Cruz, raja@ucolick.org
Address: Astronomy Department, 1156 High Street, Santa Cruz, CA 95064, USA

CoI: Rachael L. Beaton (Co-PI), University of Virginia
CoI: Karoline M. Gilbert, NOAO
CoI: Martha Boyer, Space Telescope Science Institute
CoI: Kathryn Johnston, Columbia University
CoI: Rob Swaters, NOAO
CoI: Elisa Toloba, UC-Santa Cruz/Lick Observatory
CoI: Masashi Chiba, Tohoku University
CoI: Arjun Dey, NOAO
CoI: Jason Kalirai, Space Telescope Science Institute
CoI: Evan Kirby, California Institute of Technology
CoI: Steven R. Majewski, University of Virginia
CoI: Knut A. G. Olsen, NOAO
CoI: Ricky Patterson, University of Virginia
CoI: Mikito Tanaka, Tohoku University

Title: NEWFIRM Survey of Intermediate Age Populations in M31's Halo: A Test of (Lambda)CDM

Abstract: Owing to their long dynamical times, galaxy stellar halos provide unique insight into their formation history. Recent detailed hydrodynamical and N-body simulations, carried out within the framework of a (Lambda)CDM cosmogony, can track the formation of single Milky Way sized galaxies. It is clear from these simulations that halo stars can have three distinct origins: accretion of satellites, \it in situ formation, and kicked up disk. Studies of these populations in the Milky Way are complicated by our internal perspective, but the Andromda galaxy (M31) offers the ideal combination of an external global perspective and detail. Our SPLASH team used KPNO/4-m+MOSAIC optical (M, T_2, DDO51) imaging of 72 fields and Keck/DEIMOS spectroscopy of a few \times 10^4 RGB stars across this area to discover the true metal-poor halo of M31 and has measured key properties out to 2/3 of the virial radius (R~200 kpc): surface brightness profile, substructure, kinematics, [Fe/H], and [(alpha)/Fe]. By adding to this our proposed KPNO/4-m+NEWFIRM wide-field near-infrared (J, K_s) imaging survey of intermediate-age AGB stars, we will obtain the critical missing piece for testing halo formation models: a constraint on the stellar age distribution in M31's halo.


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