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Inside the whale: the structure and dynamics of the isolated Cetus dwarf spheroidal

Lewis, G. F. and Ibata, R. A. and Chapman, S. C. and McConnachie, A. and Irwin, M. J. and Tolstoy, E. and Tanvir, N. R. (2007) Inside the whale: the structure and dynamics of the isolated Cetus dwarf spheroidal. Monthly Notices of the Royal Astronomical Society, 375 (4). pp. 1364-1370. ISSN 0035-8711. doi:10.1111/j.1365-2966.2007.11395.x.

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This paper presents a study of the Cetus dwarf, an isolated dwarf galaxy within the Local Group. A matched-filter analysis of the INT/WFC imaging of this system reveals no evidence for significant tidal debris that could have been torn off the galaxy, bolstering the hypothesis that Cetus has never significantly interacted with either the Milky Way or M31. Additionally, Keck/Deimos spectroscopic observations identify this galaxy as a distinct kinematic population possessing a systematic velocity of −87 ± 2 km s^(−1) and with a velocity dispersion of 17 ± 2 km s^(−1); while tentative, these data also suggest that Cetus possesses a moderate rotational velocity of ~8 km s^(−1). The population is confirmed to be relatively metal-poor, consistent with [Fe/H]~−1.9, and, assuming virial equilibrium, implies that the Cetus dwarf galaxy possesses a mass-to-light ratio of ~70. It appears, therefore, that Cetus may represent a primordial dwarf galaxy, retaining the kinematic and structural properties lost by other members of the dwarf population of the Local Group in their interactions with the large galaxies. An analysis of Cetus' orbit through the Local Group indicates that it is at apocentre; taken in conjunction with the general dwarf population, this shows the mass of the Local Group to be ≳ 2 × 10^(12) M_⊙.

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Additional Information:© 2007 The Authors. Journal compilation © 2007 RAS. Accepted 2006 December 11. Received 2006 December 6; in original form 2006 October 23. The anonymous referee is thanked for suggestions which improved this paper. GFL acknowledges the support of the Discovery Project grant DP0343508, and the Aspen Centre for Physics, at which some of the analysis presented in this paper was undertaken. Data presented herein were obtained using the W. M. Keck Observatory, which is operated as a scientific partnership among Caltech, the University of California and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. GFL thanks QANTAS for his upgrade on QF8, allowing him to use his laptop effectively on a trans-pacific flight and write a substantial proportion of this paper.
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Discovery ProjectDP0343508
Aspen Centre for PhysicsUNSPECIFIED
Subject Keywords:galaxies : dwarf; galaxies : individual : Cetus; Local Group
Issue or Number:4
Record Number:CaltechAUTHORS:20100204-155352779
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17391
Deposited By: Tony Diaz
Deposited On:09 Feb 2010 03:06
Last Modified:08 Nov 2021 23:35

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