The Formation and Evolution of Candidate Young Globular Clusters in NGC 3256

Abstract

We present images of the recent galaxy merger NGC 3256 obtained with the Wide Field Planetary Camera 2 of the Hubble Space Telescope in B and I filters. We show that there is a large population of more than 1000 compact, bright, blue objects in this galaxy within the 7 kpcx7 kpc region studied. These objects have sizes, colors, and luminosities like those expected for young Galactic globular clusters, with ages ranging from a few to several hundred megayears. On this basis, we identify at least some fraction of the compact, bright, blue objects in NGC 3256 as young globular clusters. The young cluster system makes up a significant fraction of the total luminosity of the galaxy within the region studied-15%-20% in B and half that in I, indicating a high efficiency of cluster formation on a galaxy-wide scale. In order to determine the properties of this young cluster system, the selection effects in size, color, and luminosity are carefully modeled. We find that the intrinsic color distribution is broad and there is no significant trend of color with magnitude. The combination of the broad range of observed colors and the lack of a trend of redder colors at fainter magnitudes cannot be fitted solely by a broad age distribution and/or differential reddening, although the latter is clearly present. The observations can be accounted for by either the preferential depletion/destruction of lower mass clusters as they age or a very young age (