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Date and Time of the Query: 2019-04-25 T01:22:16 PDT
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For refcode 2009ApJ...690..512H:
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2009ApJ...690..512H Low-Mass X-Ray Binaries and Globular Clusters in Early-Type Galaxies. II. Globular Cluster Candidates and Their Mass-Metallicity Relation Humphrey, Philip J. Abstract. We present an astrometry and photometry catalogue of globular cluster (GC) candidates detected with the Hubble Space Telescope Wide Field Planetary Camera 2 in a sample of 19 early-type galaxies, appropriate for comparison with the low-mass X-ray binary populations observed with Chandra. In a companion paper, we present the Chandra data and investigate the relation between these populations. We demonstrate that, although there is little evidence of a color-magnitude correlation for the GCs, after estimating mass and metallicity from the photometry under the assumption of a single-age simple stellar population, there is a significant positive correlation between mass and metallicity. We constrained [Z/H] = (-2.1 +/- 0.2) + (0.25 +/- 0.04)log_10_M, with a 1{sigma} intrinsic scatter of 0.62 dex in metallicity. If GCs are bimodal in metallicity, this relation is consistent with recent suggestions of a mass-metallicity relation only for metal-poor clusters. Adopting a new technique to fit the GC luminosity function (GCLF) accounting for incompleteness and the Eddington bias, we compute the V-band local GC specific frequency (S_N_) and specific luminosity (S_L_) of each galaxy. We show that S_L_ is the more robust measure of the richness of a GC population where a significant fraction is undetected due to source detection incompleteness. We find that the absolute magnitude of the GCLF turnover exhibits intrinsic scatter from galaxy to galaxy of ~0.3 mag (1{sigma}), limiting its accuracy as a standard distance measure. Key words: galaxies: distances and redshifts, galaxies: elliptical and lenticular, cD, galaxies: general, galaxies: star clusters
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