THE COLOR-MAGNITUDE RELATION FOR METAL-POOR GLOBULAR CLUSTERS IN M87: CONFIRMATION FROM DEEP HST/ACS IMAGING

Peng, EW; Jordán A.; Blakeslee, JP; Mieske S.; Côté P.; Ferrarese, L; HARRIS, WE; Madrid, JP; Meurer, GR

Abstract

Metal-poor globular clusters (GCs) are our local link to the earliest epochs of star formation and galaxy building. Studies of extragalactic GC systems using deep, high-quality imaging have revealed a small but significant slope to the color-magnitude relation for metal-poor GCs in a number of galaxies. We present a study of the M87 GC system using deep, archival HST/ACS imaging with the F606W and F814W filters, in which we find a significant color-magnitude relation for the metal-poor GCs. The slope of this relation in the I versus V-I color-magnitude diagram (?I = -0.024 0.006) is perfectly consistent with expectations based on previously published results using data from the ACS Virgo Cluster Survey. The relation is driven by the most luminous GCs, those with MI ? -10, and its significance is largest when fitting metal-poor GCs brighter than MI = -7.8, a luminosity which is 1 mag fainter than our fitted Gaussian mean for the luminosity function (LF) of blue, metal-poor GCs (0.8 mag fainter than the mean for all GCs). These results indicate that there is a mass scale at which the correlation begins, and is consistent with a scenario where self-enrichment drives a mass-metallicity relationship. We show that previously measured half-light radii of M87 GCs from best-fit PSF-convolved King models are consistent with the more accurate measurements in this study, and we also explain how the color-magnitude relation for metal-poor GCs is real and cannot be an artifact of the photometry. We fit Gaussian and evolved Schechter functions to the luminosity distribution of GCs across all colors, as well as divided into blue and red subpopulations, finding that the blue GCs have a brighter mean luminosity and a narrower distribution than the red GCs. Finally, we present a catalog of astrometry and photometry for 2250 M87 GCs. © 2009. The American Astronomical Society. All rights reserved.

Más información

Título según WOS: THE COLOR-MAGNITUDE RELATION FOR METAL-POOR GLOBULAR CLUSTERS IN M87: CONFIRMATION FROM DEEP HST/ACS IMAGING
Título según SCOPUS: The color?magnitude relation for metal-poor globular clusters in m87: Confirmation from deep hst/acs imaging
Título de la Revista: ASTROPHYSICAL JOURNAL
Volumen: 703
Número: 1
Editorial: IOP PUBLISHING LTD
Fecha de publicación: 2009
Página de inicio: 42
Página final: 51
Idioma: English
URL: http://stacks.iop.org/0004-637X/703/i=1/a=42?key=crossref.012d04887d97478d848706d4ad22bca3
DOI:

10.1088/0004-637X/703/1/42

Notas: ISI, SCOPUS