Please use this identifier to cite or link to this item:
Title: A spectroscopic survey of EC4, an extended cluster in Andromeda's halo
Authors: Collins, M. L. M.
Chapman, S. C.
Irwin, M.
Ibata, R.
Martin, N. F.
Ferguson, A. M. N.
MacKey, A. D.
Huxor, A.
Lewis, G. F.
McConnachie, A. W.
Tanvir, N.
First Published: 1-Jul-2009
Publisher: Oxford University Press (OUP)
Citation: Monthly Notices of the Royal Astronomical Society, 2009, 396 (3), pp. 1619-1628
Abstract: We present a spectroscopic survey of candidate red giant branch stars in the extended star cluster, EC4, discovered in the halo of M31 from our Canada—France—Hawaii Telescope/MegaCam survey, overlapping the tidal streams, Streams ‘Cp’ and ‘Cr’. These observations used the DEep Imaging Multi–Object Spectrograph mounted on the Keck II telescope to obtain spectra around the Caii triplet region with ∼1.3 Å resolution. Six stars lying on the red giant branch within two core radii of the centre of EC4 are found to have an average vr=−287.9+1.9−2.4 km s−1 and σv,corr = 2.7+4.2−2.7 km s−1, taking instrumental errors into account. The resulting mass–to–light ratio for EC4 is M/L = 6.7+15−6.7 M⊙/L⊙, a value that is consistent with a globular cluster within the 1σ errors we derive. From the summed spectra of our member stars, we find EC4 to be metal–poor, with [Fe/H]=−1.6 ± 0.15. We discuss several formation and evolution scenarios which could account for our kinematic and metallicity constraints on EC4, and conclude that EC4 is most comparable with an extended globular cluster. We also compare the kinematics and metallicity of EC4 with Streams ‘Cp’ and ‘Cr’, and find that EC4 bears a striking resemblance to Stream ‘Cp’ in terms of velocity, and that the two structures are identical in terms of both their spectroscopic and photometric metallicities. From this, we conclude that EC4 is likely related to Stream ‘Cp’.
DOI Link: 10.1111/j.1365-2966.2009.14830.x
ISSN: 0035-8711
eISSN: 1365-2966
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2009 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Deposited with reference to the publisher’s archiving policy available on the SHERPA/RoMEO website.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

Files in This Item:
File Description SizeFormat 
MNRAS-2009-Collins-1619-28.pdfPublished (publisher PDF) 412.61 kBAdobe PDFView/Open

Items in LRA are protected by copyright, with all rights reserved, unless otherwise indicated.