The extended disc and halo of the andromeda galaxy observed with spitzer-IRAC

Authors

Masoud Rafiei Ravandi, The University of Western Ontario
Pauline Barmby, The University of Western Ontario
Matthew L.N. Ashby, Harvard-Smithsonian Center for Astrophysics
Seppo Laine, Spitzer Science Center
T. J. Davidge, National Research Council Canada
Jenna Zhang, Harvard-Smithsonian Center for Astrophysics
Luciana Bianchi, Johns Hopkins University
Arif Babul, University of Victoria
S. C. Chapman, Dalhousie University

Document Type

Article

Publication Date

6-21-2016

Journal

Monthly Notices of the Royal Astronomical Society

Volume

459

Issue

2

First Page

1403

Last Page

1414

URL with Digital Object Identifier

10.1093/mnras/stw652

Abstract

We present the first results from an extended survey of the Andromeda galaxy (M31) using 41.1 h of observations by Spitzer-IRAC at 3.6 and 4.5 μm. This survey extends previous observations to the outer disc and halo, covering total lengths of 4˙ 4 and 6˙6 along the minor and major axes, respectively. We have produced surface brightness profiles by combining the integrated light from background-corrected maps with stellar counts from a new catalogue of point sources. Using auxiliary catalogues, we have carried out a statistical analysis in colour-magnitude space to discriminate M31 objects from foreground Milky Way stars and background galaxies. The catalogue includes 426 529 sources, of which 66 per cent have been assigned probability values to identify M31 objects with magnitude depths of [3.6]=19.0±0.2, [4.5]=18.7±0.2.We discuss applications of our data for constraining the stellar mass and characterizing point sources in the outer radii.