| Abstrakt: |
We study the fraction of tidal interactions and mergers (TIMs) with well-identified observability timescales (fTIM) in group, cluster, and accompanying field galaxies and its dependence on redshift (z), cluster velocity dispersion (σ), and environment analyzing Hubble Space Telescope/ACS images and catalogs from the ESO Distant Cluster Survey. Our sample consists of 11 clusters, seven groups, and accompanying field galaxies at 0.4 ≤ z ≤ 0.8. We derive fTIM using both a visual classification of galaxy morphologies and an automated method, the G − M20 method. We calibrate this method using the visual classifications that were performed on a subset of our sample. We find marginal evidence for a trend between fTIM and z, in that higher z values correspond to higher fTIM. However, we also cannot rule out the null hypothesis of no correlation at higher than 68% confidence. No trend is present between fTIM and σ. We find that fTIM shows suggestive peaks in groups, and tentatively in clusters at R > 0.5 × R200, implying that fTIM gets boosted in these intermediate-density environments. However, our analysis of the local densities of our cluster sample does not reveal a trend between fTIM and density, except for a potential enhancement at the very highest densities. We also perform an analysis of projected radius–velocity phase space for our cluster members. Our results reveal that TIM and undisturbed galaxies only have a 6% probability of having been drawn from the same parent population in their velocity distribution and 37% in radii, in agreement with the modest differences obtained in fTIM at the clusters. [ABSTRACT FROM AUTHOR] |
