Metal Abundance Properties of M81 Globular Cluster System

Kavli Affiliate: Jiansheng Chen

| First 5 Authors: Jun Ma, David Burstein, Zhou Fan, Xu Zhou, Jiansheng Chen

| Summary:

This paper is the third in the series of papers on M81 globular clusters. In
this paper, we present spatial and metal abundance properties of 95 M81
globular clusters, which comprise nearly half of all the M81 globular cluster
system. These globular clusters are divided into two M81 metallicity groups by
a KMM test. Our results show that, the metal-rich clusters did not demonstrate
a centrally concentrated spatial distribution as ones in M31, and metal-poor
clusters tend to be less spatially concentrated. In other words, the
distribution of the metal-rich clusters in M81 is not very similar to that of
M31. Most of the metal-rich clusters distribute at projected radii of 4-8 kpc.
It is also noted that the metal-rich clusters distribute within the inner 20
kpc, and the metal-poor ones do out to radii of ~40 kpc. Like our Galaxy and
M31, the metallicity distribution of globular clusters in M81 along
galactocentric radius suggests that some dissipation occurred during the
formation of the globular cluster system, i.e. smooth, pressure-supported
collapse models of galaxies are unlikely to produce such radial distribution of
metallicity presented in this paper. There is not evident correlation between
globular cluster luminosity and metallicity in M81 globular clusters. The
overwhelming conclusion of this paper seems to be that a more complete and
thorough cluster search is needed in M81.

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