NOAO >   Observing Info >   Approved Programs >   2012B-0098

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Proposal Information for 2012B-0098


PI: R. Michael Rich, University of California Los Angeles, rmr@astro.ucla.edu
Address: Physics Department, 430 Portola Plaza, Los Angeles 90095, USA

CoI: Andreas Koch, Landessternwarte, University of Heidelberg
CoI: Benjamin Hendricks, Landessternwarte, University of Heidelberg

Title: Hydra I: an odd, double-lobed ``globular cluster''

Abstract: We propose to obtain radial velocity and metallicity measurements using the calcium triplet in stars of the nearby (9.7 kpc) Hydra I system, which has been claimed to be a massive globular cluster in the last stages of tidal disruption. While its size and preliminary velocity dispersion are unusually large and reminiscent of an accreted dwarf galaxy, the associated stellar stream is remarkably narrow. The most puzzling feature of this object is, however, its morphology, which shows two clearly separated lobes (each with a radius of ~30") of unknown origin. Measurements of the kinematics and metallicity of large numbers of stars spread over a large area on this cluster and within the stream provide the only means to look for possible velocity or abundance gradients, to characterize possible population differences, and to trace the origin and fate of this peculiar system. Furthermore, we can address how the main body relates to the kinematics of the stream and what we can thus infer about its orbit and evolution.


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NOAO >   Observing Info >   Approved Programs >   2012B-0098

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