The globular cluster system of the virgo giant elliptical galaxy NGC 4636. i. subaru/faint object camera and spectrograph spectroscopy and database

Abstract

We present a spectroscopic study of the globular clusters (GCs) in the giant elliptical galaxy NGC4636 in the Virgo Cluster. We selected target GC candidates using the Washington photometry derived from the deep CCD images taken at the KPNO 4 m Telescope. Then we obtained the spectra of 164 target objects in the field of NGC4636 using the Multi-Object Spectroscopy mode of Faint Object Camera and Spectrograph on the Subaru 8.2m Telescope. We have measured the velocities for 122 objects: 105 GCs in NGC4636, the nucleus of NGC4636, 11 foreground stars, two background galaxies, and three probable intracluster GCs in the Virgo Cluster. The GCs in NGC4636 are located in the projected galactocentric radius within 10′ (corresponding to 43kpc). The measured velocities for the GCs range from 300 km s-1 to 1600 km s-1, with a mean value of 932+25-22 km s -1, which is in good agreement with the velocity for the nucleus of NGC4636, 928 45 km s-1. The velocity dispersion of the GCs in NGC4636 is derived to be 231+15-17 km s-1, and the velocity dispersion of the blue GCs is slightly larger than that of the red GCs. Combining our results with data in the literature, we produce a master catalog of radial velocities for 238 GCs in NGC4636. The velocity dispersion of the GCs in the master catalog is found to be 225+12-9 km s -1 for the entire sample, 251+18-12 km s -1 for 108 blue GCs, and 205+11-13 km s -1 for 130 red GCs. © 2010 The American Astronomical Society.