Tidal stripping of globular clusters in the Virgo cluster.
COENDA V., MURIEL H. and DONZELLI C.
Abstract (from CDS):
With the aim of finding evidence of tidal stripping of globular clusters (GCs) we analyzed a sample of 13 elliptical galaxies taken from the ACS Virgo Cluster Survey (VCS). These galaxies belong to the main concentration of the Virgo Cluster (VC) and present absolute magnitudes -18.5 < Mz< -22.5. We used the public GC catalog of Jordán et al. and separated the GC population into metal poor (blue) and metal rich (red) according to their integrated colors. The galaxy properties were taken from Peng et al. We found the following. (1) The specific frequencies (SN) of total and blue GC populations increase as a function of the projected galaxy distances rp to M87. A similar result is observed when three-dimensional distances r3D are used. The same behaviors are found if the analysis is made using the number of GCs per (T). No correlations between SN or T and rpor r3Dis observed for the red GC population. The correlations for the blue GCs (typically more extended) and the lack of correlations for the red GCs (more concentrated) with the clustocentric distance of the host galaxy are interpreted as evidence of GCs stripping due to tidal forces. (2) No correlation is found between the slope of GC density profiles of host galaxies and the galaxy distance to M87 (Virgo central galaxy). The lack of such a correlation is interpreted in terms of a shrinkage of the GC distribution after the stripping of GCs in the outermost region of galaxies. (3) We also computed the local density of GCs (ρout) located further than 6.2 kpc from the galaxy center for nine galaxies of our sample. We find that the GC population around most of these galaxies is mainly composed of blue GCs. The two highest values of ρout are found in the core of the VC (up to 100 kpc) and correspond to the two lowest values of SN. Our results suggest that the number and the fraction of blue and red GCs observed in elliptical galaxies located near the centers of massive clusters could be significantly different from the underlying GC population. These differences could be explained by tidal stripping effects that occur as galaxies approach the centers of clusters.
galaxies: clusters: general - galaxies: elliptical and lenticular, cD - galaxies: interactions - globular clusters: general