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Date and Time of the Query: 2019-05-25 T01:24:16 PDT
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For refcode 2006ApJ...639...95P:
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Copyright by American Astronomical Society. Reproduced by permission
2006ApJ...639...95P The ACS Virgo Cluster Survey. IX. The Color Distributions of Globular Cluster Systems in Early-Type Galaxies Eric W. Peng, Andres Jordan, Patrick Cote, John P. Blakeslee, Laura Ferrarese, Simona Mei, Michael J. West, David Merritt, Milos Milosavljevic, and John L. Tonry Abstract. We present the color distributions of globular cluster (GC) systems for 100 early-type galaxies observed in the ACS Virgo Cluster Survey, the deepest and most homogeneous survey of this kind to date. On average, galaxies at all luminosities in our study (-22<M_B_<-15) appear to have bimodal or asymmetric GC color distributions. Almost all galaxies possess a component of metal-poor GCs, with the average fraction of metal-rich GCs ranging from 15% to 60% and increasing with luminosity. The colors of both subpopulations correlate with host galaxy luminosity and color, with the red GCs having a steeper slope. To convert color to metallicity, we introduce a preliminary (g-z)-[Fe/H] relation calibrated to Galactic, M49, and M87 GCs. This relation is nonlinear, with a steeper slope for [Fe/H]<~-0.8. As a result, the metallicities of the metal-poor and metal-rich GCs vary similarly with respect to galaxy luminosity and stellar mass, with relations of [Fe/H]_MP_ is proportional to L^0.16+/-0.04^ is proportional to M^0.17+/-0.04^_*_ and [Fe/H]_MR_ is proportional to L^0.26+/-0.03^ is proportional to M^0.22+/-0.03^_*_, respectively. Although these relations are shallower than the mass-metallicity relation predicted by wind models and observed for dwarf galaxies, they are very similar to the relation observed for star-forming galaxies in the same mass range. The offset between the two GC populations is approximately 1 dex across 3 orders of magnitude in mass, suggesting a nearly universal amount of enrichment between the formation of the two populations of GCs. We also find that although the metal-rich GCs show a larger dispersion in color, it is the metal-poor GCs that have an equal or larger dispersion in metallicity. The similarity in the M_*_ -- [Fe/H] relations for the two populations implies that the conditions of GC formation for metal-poor and metal-rich GCs could not have been too different. Like the color-magnitude relation, these relations derived from globular clusters present stringent constraints on the formation and evolution of early-type galaxies. Key words: Galaxies: Elliptical and Lenticular, cD, Galaxies: Evolution, Galaxies: Star Clusters, Galaxy: Globular Clusters: General
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