Chapman, S. C. and Ibata, R. and Irwin, M. and Koch, A. and Letarte, B. and Martin, N. and Collins, M. and Lewis, G. F. and McConnachie, A. and Peñarrubia, J. and Rich, R. M. and Trethewey, D. and Ferguson, A. and Huxor, A. and Tanvir, N. (2008) The kinematic footprints of five stellar streams in Andromeda's halo. Monthly Notices of the Royal Astronomical Society, 390 (4). pp. 1437-1452. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:CHAmnras08
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We present a spectroscopic analysis of five stellar streams ('A', 'B', 'Cr', 'Cp' and 'D') as well as the extended star cluster, EC4, which lies within Stream 'C', all discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey. These spectroscopic results were initially serendipitous, making use of our existing observations from the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope, and thereby emphasizing the ubiquity of tidal streams that account for similar to 70 per cent of the M31 halo stars in the targeted fields. Subsequent spectroscopy was then procured in Stream 'C' and Stream 'D' to trace the velocity gradient along the streams. Nine metal-rich ([Fe/H] similar to -0.7) stars at v(hel) = -349.5 km s(-1), sigma(v,corr) similar to 5.1 +/- 2.5 km s(-1) are proposed as a serendipitous detection of Stream 'Cr', with follow-up kinematic identification at a further point along the stream. Seven metal-poor ([Fe/H] similar to-1.3) stars confined to a narrow, 15 km s(-1) velocity bin centred at v(hel) = -285.6, sigma(v,corr) = 4.3(-1.4)(+1.7) km s(-1) represent a kinematic detection of Stream 'Cp', again with follow-up kinematic identification further along the stream. For the cluster EC4, candidate member stars with average [Fe/H] similar to-1.4, are found at v(hel) = -282 suggesting it could be related to Stream 'Cp'. No similarly obvious cold kinematic candidate is found for Stream 'D', although candidates are proposed in both of two spectroscopic pointings along the stream (both at similar to -400 km s(-1)). Spectroscopy near the edge of Stream 'B' suggests a likely kinematic detection at v(hel) similar to -330, sigma(v,corr) similar to 6.9 km s(-1), while a candidate kinematic detection of Stream 'A' is found (plausibly associated to M33 rather than M31) with v(hel) similar to -170, sigma(v,corr) = 12.5 km s(-1). The low dispersion of the streams in kinematics, physical thickness and metallicity makes it hard to reconcile with a scenario whereby these stream structures as an ensemble are related to the giant southern stream. We conclude that the M31 stellar halo is largely made up of multiple kinematically cold streams.
|Additional Information:||© 2008 The Authors. Journal compilation © 2008 RAS. Accepted 2008 July 8. Received 2008 June 16; in original form 2008 March 26. Published Online: 15 October 2008. We thank an anonymous referee for a very careful reading and a helpful report. We thank Mark Fardal for helpful discussions on the giant southern stream. SCC acknowledges NSERC and the Canadian Space Agency for support. RMR and AK acknowledge support from AST-0309731. 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.|
|Subject Keywords:||stars: kinematics; galaxies: haloes; galaxies: individual: M31|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||15 Jan 2009 06:24|
|Last Modified:||26 Dec 2012 10:32|
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