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A near-zero velocity dispersion stellar component in the Canes Venatici dwarf spheroidal galaxy

Ibata, R. and Chapman, S. and Irwin, M. and Lewis, G. and Martin, N. (2006) A near-zero velocity dispersion stellar component in the Canes Venatici dwarf spheroidal galaxy. Monthly Notices of the Royal Astronomical Society, 373 (1). L70-L74. ISSN 0035-8711.

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We present a spectroscopic survey of the newly discovered Canes Venatici dwarf galaxy using the Keck/DEIMOS spectrograph. Two stellar populations of distinct kinematics are found to be present in this galaxy: an extended, metal-poor component, of half-light radius 7.8(-2.1)(+2.4) arcmin, which has a velocity dispersion of 13.9(-2.5)(+3.2) km s^(-1), and a more concentrated (half-light radius 3.6(-0.8)(+1.1) arcmin) metal-rich component of extremely low velocity dispersion. At 99 per cent confidence, the upper limit to the central velocity dispersion of the metal-rich population is 1.9 km s^(-1). This is the lowest velocity dispersion ever measured in a galaxy. We perform a Jeans analysis on the two components, and find that the dynamics of the structures can only be consistent if we adopt extreme (and unlikely) values for the scalelength and velocity dispersion of the metal-poor population. With a larger radial velocity sample and improved measurements of the density profile of the two populations, we anticipate that it will be possible to place strong constraints on the central distribution of the dark matter in this galaxy.

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Martin, N.0000-0002-1349-202X
Additional Information:© 2006 The Authors. Journal compilation © 2006 RAS. Accepted 2006 September 4. Received 2006 August 31; in original form 2006 August 6. The author would like to thank the hospitality of the Aspen Center for Physics, where a large portion of the analysis of this paper was undertaken. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. This paper has been typeset from a TEX/LATEX file prepared by the author.
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W. M. Keck FoundationUNSPECIFIED
Subject Keywords:galactic kinematics and dynamics; Local Group; dark matter
Issue or Number:1
Record Number:CaltechAUTHORS:IBAmnras06
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11247
Deposited By: Tony Diaz
Deposited On:06 Aug 2008 04:22
Last Modified:03 Oct 2019 00:17

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