NOAO >   Observing Info >   Approved Programs >   2012B-0209

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Proposal Information for 2012B-0209


PI: Beth Willman, Haverford College, bwillman@haverford.edu
Address: Astronomy Department, 370 Lancaster Avenue, Haverford, PA 19041, USA

CoI: Andrew West, Boston University

Title: Investigating Overdensities of Cool Stars at the Edge of the Milky Way

Abstract: We propose to use Gemini/GNIRS to observe stars belonging to four localized overdensities of cool stars in the Milky Way. The proposed spectroscopic program will determine whether the stars in the overdensities are dwarfs or giants, and will provide their radial velocities. If these overdensities are composed of cool giant stars, then they reside at outer halo (200 - 600 kpc) distances with physical sizes of 500 pc - 1 kpc, consistent with them being dwarf galaxies (or the remnants thereof). If these overdensities are composed of cool dwarf stars, then they reside at nearby (500 pc - 2 kpc) distances with physical sizes of a few parsec, consistent with them being low surface brightness star clusters, or the remnants thereof. Independent of whether these previously unseen structures are composed of dwarf or giant stars, their presence and origin may have far-reaching ramifications for the history and evolution of the Milky Way.


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