THE M33 GLOBULAR CLUSTER SYSTEM WITH PAndAS DATA: THE LAST OUTER HALO CLUSTER?

Journal Article · Fri Apr 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/730/2/112· OSTI ID:21574841

Cockcroft, Robert; Harris, William E ^[1]; Ferguson, Annette M. N., ^[2]

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1. Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)
2. Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)

We use CFHT/MegaCam data to search for outer halo star clusters in M33 as part of the Pan-Andromeda Archaeological Survey. This work extends previous studies out to a projected radius of 50 kpc and covers over 40 deg{sup 2}. We find only one new unambiguous star cluster in addition to the five previously known in the M33 outer halo (10 kpc {<=} r {<=} 50 kpc). Although we identify 2440 cluster candidates of various degrees of confidence from our objective image search procedure, almost all of these are likely background contaminants, mostly faint unresolved galaxies. We measure the luminosity, color, and structural parameters of the new cluster in addition to the five previously known outer halo clusters. At a projected radius of 22 kpc, the new cluster is slightly smaller, fainter, and redder than all but one of the other outer halo clusters, and has g' {approx} 19.9, (g' - i') {approx} 0.6, concentration parameter c {approx} 1.0, a core radius r{sub c} {approx} 3.5 pc, and a half-light radius r{sub h} {approx} 5.5 pc. For M33 to have so few outer halo clusters compared to M31 suggests either tidal stripping of M33's outer halo clusters by M31, or a very different, much calmer accretion history of M33.

• OSTI ID: 21574841
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 730; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
LUMINOSITY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
STAR CLUSTERS