The effect of second generation populations on the integrated colors of metal-rich globular clusters in early-type galaxies

Abstract

The mean color of globular clusters (GCs) in early-type galaxies is in general bluer than the integrated color of halo field stars in host galaxies. Metal-rich GCs often appear more associated with field stars than metal-poor GCs, yet show bluer colors than their host galaxy light. Motivated by the discovery of multiple stellar populations in Milky Way GCs, we present a new scenario in which the presence of second-generation (SG) stars in GCs is responsible for the color discrepancy between metal-rich GCs and field stars. The model assumes that the SG populations have enhanced helium abundance as evidenced by observations, and it gives a good explanation of the bluer optical colors of metal-rich GCs than field stars as well as strong Balmer lines and blue UV colors of metal-rich GCs. Ours may be complementary to the recent scenario suggesting the difference in stellar mass functions (MFs) as an origin for the GC-to-star color offset. A quantitative comparison is given between the SG and MF models.

12 pages, 3 figures, 1 table, accepted for publication in the ApJL

References in corpus (6)

• A systematic variation of the stellar initial mass function in early-type galaxies
• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• A Quantitative Link Between Globular Clusters and the Stellar Halos in Elliptical Galaxies
• UV Bright Globular Clusters in M87: More Evidence for Super-helium-rich Stellar Populations?
• The Optical Colors of Giant Elliptical Galaxies and their Metal-Rich Globular Clusters Indicate a Bottom-Heavy Initial Mass Function
• Evidence for Two Distinct Stellar Initial Mass Functions : Revisiting the Effects of Cluster Dynamical Evolution

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• Yonsei Evolutionary Population Synthesis (YEPS) Model. III. Surface Brightness Fluctuation of Normal and Helium-enhanced Simple Stellar Populations
• Multivariate analysis of the globular clusters in M87
• Comparisons of Different Fitting Methods for the Physical Parameters of A Star Cluster Sample of M33 with Spectroscopy and Photometry
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• On the Use of the Number Count of Blue Horizontal--Branch Stars to Infer the Dominant Building Blocks of the Milky Way Halo
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• Nonlinear Color-Metallicity Relations of Globular Clusters. XI. Nonlinearity Effect Revealed by NGC 5128 (Centaurus A) and NGC 4594 (Sombrero) Galaxies