Near-Infrared Color-Metallicity Relation for Globular Cluster System in Elliptical Galaxy NGC 4649

  • Jeong, Jong-Hoon (Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University) ;
  • Kim, Sooyoung (Korea Astronomy and Space Science Institute) ;
  • Yoon, Suk-Jin (Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University)
  • Published : 2017.10.10

Abstract

We present Subaru Near-Infrared (NIR) photometry for globular clusters (GCs) in the giant elliptical galaxy NGC 4649 (M60) belonging to the Virgo cluster. NIR data are obtained in Ks-band with the Subaru/MOIRCS, and matching HST/ACS optical data available in literature are used to explore the origin of GC color bimodality. A clear bimodal color distribution is observed in the optical color (g-z), in which the ratio between blue and red GCs is 4:6. By contrast, the more metallicity-sensitive optical-NIR colors (g-Ks, z-Ks) show a considerably weakened bimodality in their distributions. The color-color relation of the optical and NIR colors for the GC system shows a nonlinear feature, supporting that the optical color bimodality observed in NGC 4649 GC system is caused by nonlinear color-metallicity relations (CMRs).

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