Tidal Stripping of Globular Clusters in the Virgo Cluster

TL;DR

This study provides evidence that tidal forces in the Virgo cluster strip globular clusters from elliptical galaxies, especially affecting blue GCs, and alters their observed populations near the cluster center.

Contribution

It demonstrates a correlation between GC populations and galaxy distance to M87, indicating tidal stripping effects in a galaxy cluster environment.

Findings

Specific frequencies of GCs increase with galaxy distance from M87.

No correlation between GC density profile slopes and galaxy distance.

Blue GCs dominate the outer regions of galaxies near cluster centers.

Abstract

With the aim of finding evidence of tidal stripping of globular clusters (GCs) we analysed 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 $-18.5<M_z<-22.5$. We used the public GC catalog of Jord\'an et al. (2008) and separated the GC population into metal poor (blue) and metal rich (red) according to their integrated colors. The galaxy properties were taken from \citet{Peng:2008}. We found that: 1) The specific frequencies ($S_N$) of total and blue GC populations increase as a function of the projected galaxy distances $r_p$ to M87. A similar result is observed when 3-dimensional distances $r_{3D}$ are used. The same behaviours are found if the analysis are made using the number of GCs per $10^9\Msun$ ($T$). The correlations 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). 3) We also computed the local density of GCs ($\rho_{out}$) 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. 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.