Washington CCD Photometry of the Globular Cluster System of the Giant Elliptical Galaxy M60 in Virgo

Citations Over TimeTop 10% of 2008 papers

Abstract

We present a photometric study of the globular clusters in the giant elliptical galaxy M60 in the Virgo cluster, based on deep, relatively wide field Washington CT_1 CCD images. The color-magnitude diagram reveals a significant population of globular clusters in M60, and a large number of young luminous clusters in NGC 4647, a small companion spiral galaxy north-west of M60. The color distribution of the globular clusters in M60 is clearly bimodal, with a blue peak at (C-T_1)=1.37, and a red peak at (C-T_1)=1.87. We derive two new transformation relations between the (C-T_1)_0 color and [Fe/H] using the data for the globular clusters in our Galaxy and M49. Using these relations we derive the metallicity distribution of the globular clusters in M60, which is also bimodal: a dominant metal-poor component with center at [Fe/H]=-1.2, and a weaker metal-rich component with center at [Fe/H]=-0.2. The radial number density profile of the globular clusters is more extended than that of the stellar halo, and the radial number density profile of the blue globular clusters is more extended than that of the red globular clusters. The number density maps of the globular clusters show that the spatial distribution of the blue globular clusters is roughly circular, while that of the red globular cluster is elongated similarly to that of the stellar halo. We estimate the total number of the globular clusters in M60 to be 3600+/-500$,and the specific frequency to be S_N=3.8+/-0.4. The mean color of the bright blue globular clusters gets redder as they get brighter in both the inner and outer region of M60. This blue tilt is seen also in the outer region of M49, the brightest Virgo galaxy. Implications of these results are discussed.

Related Papers

• → The 'Red Giant Clock' as an indicator for the efficiency of central mixing in horizontal-branch stars(1989)61 cited
• → The magnitude difference between the main sequence turn off and the red giant branch bump in Galactic globular clusters(2011)42 cited
• → On the red giant branch mass loss in 47 Tucanae: Constraints from the horizontal branch morphology(2016)31 cited
• → The Age‐dependent Luminosities of the Red Giant Branch Bump, Asymptotic Giant Branch Bump, and Horizontal Branch Red Clump(1999)71 cited