THE ACS FORNAX CLUSTER SURVEY. IX. THE COLOR-MAGNITUDE RELATION OF GLOBULAR CLUSTER SYSTEMS

Journal Article · Sat Feb 20 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/710/2/1672· OSTI ID:21394411

Mieske, Steffen; West, Michael J ^[1]; Jordan, Andres; Infante, Leopoldo ^[2]; Cote, Patrick; Ferrarese, Laura; Blakeslee, John P ^[3]; Peng, Eric W ^[4]; Mei, Simona ^[5]; Baumgardt, Holger ^[6]; Tonry, John L ^[7]

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1. European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile)
2. Departamento de AstronomIa y Astrofisica, Pontificia Universidad Catolica de Chile, Santiago 22 (Chile)
3. Herzberg Institute of Astrophysics, Victoria, BC V9E 2E7 (Canada)
4. Department of Astronomy, Peking University, Beijing 100871 (China)
5. University of Paris Denis Diderot, 75205 Paris Cedex 13 (France)
6. Argelander Institut fuer Astronomie, Auf dem Huegel 71, 53121 Bonn (Germany)
7. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

We investigate the color-magnitude relation for globular clusters (GCs)-the so-called blue tilt-detected in the Advanced Camera for Surveys (ACS) Fornax Cluster Survey and using the combined sample of GCs from the ACS Fornax and Virgo Cluster Surveys. We find a tilt of gamma{sub z} {identical_to} d(g - z)/dz = -0.0257 +- 0.0050 for the full GC sample of the Fornax Cluster Survey ({approx}5800 GCs). This is slightly shallower than the value gamma{sub z} = -0.0459 +- 0.0048 found for the Virgo Cluster Survey GC sample ({approx}11,100 GCs). The slope for the merged Fornax and Virgo data sets ({approx}16,900 GCs) is gamma{sub z} = -0.0293 +- 0.0085, corresponding to a mass-metallicity relation of Z {proportional_to} M {sup 0.43+}-{sup 0.12}. We find that the blue tilt sets in at masses in excess of M {approx} 2 x 10{sup 5} M{sub sun}. The tilt is stronger for GCs belonging to high-mass galaxies (M{sub *} {approx}> 5 x 10{sup 10} M{sub sun}) than for those in low-mass galaxies (M{sub *} {approx}< 5 x 10{sup 10} M{sub sun}). It is also more pronounced for GCs with smaller galactocentric distances. Our findings suggest a range of mass-metallicity relations Z{sub GC} {proportional_to} M {sup 0.3-0.7}{sub GC} which vary as a function of host galaxy mass/luminosity, a scaling similar to that observed for dwarf spheroidal galaxies. We compare our observations to a recent model of star cluster self-enrichment with generally favorable results. We suggest that, within the context of this model, the protocluster clouds out of which the GCs formed may have had density profiles slightly steeper than isothermal and/or star formation efficiencies somewhat below 0.3. We caution, however, that the significantly different appearance of the color-magnitude diagrams (CMDs) defined by the GC systems associated with galaxies of similar mass and morphological type poses a challenge to any single mechanism, including self-enrichment, that seeks to explain generically the observed GC color-magnitude relations. We therefore suggest that the detailed (and stochastic) merger/accretion histories of individual galaxies have likely played a non-negligible role determining the distribution of GCs in the CMDs of individual GC systems.

• OSTI ID: 21394411
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 710; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CAMERAS
COLOR
EVOLUTION
GALAXIES
GALAXY CLUSTERS
LUMINOSITY
MASS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
STAR CLUSTERS
STAR EVOLUTION
STARS
STOCHASTIC PROCESSES