To Be or Not to Be: Very Young Globular Clusters in M31
We present observations made with the newly commissioned Keck laser guide star adaptive optics (LGSAO) system of six objects in M31 that are alleged in multiple recent studies to be young globular clusters (GCs); all are supposed to have ages ≤5 Gyr. The resulting FWHM of the PSF core in our images is ~70 mas. The four youngest of these objects are asterisms; they are with certainty not young GCs in M31. Based on their morphology, the two oldest are GCs in M31. While the M31 GCs with ages 5-8 Gyr appear to be mostly genuine, it appears that many of the alleged very young GCs in M31 are spurious identifications. This problem will be even more severe in studies now underway of the GC systems of more distant spiral galaxies, for which imaging at the spatial resolution of our observations in M31 may not be adequate to detect sample contamination by asterisms.
Additional Information© 2005 The American Astronomical Society. Received 2005 September 2; accepted 2005 October 7; published 2005 November 1. Based in part on observations 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.
Published - Cohen_2005_ApJ_634_L45.pdf
Accepted Version - 0510631.pdf