Statistics of interacting galaxies at z~0.7

TL;DR

This study analyzes the frequency and evolution of interacting galaxies with tidal tails and M51-type features at redshifts up to 1.5, revealing a significant increase in such interactions at z<0.7 and estimating the impact on galaxy evolution.

Contribution

It provides the first statistical analysis of interacting galaxy frequencies at z~0.7 using deep HST fields, highlighting the evolution of merger rates over the last 6-7 billion years.

Findings

The space density of interacting galaxies increases as (1+z)^2.6 for z<0.7.

Approximately one-third of galaxies with M(B)<-18 mag experienced strong perturbations since z<0.7.

About 10-20% of galaxies have accreted satellites similar to M51-type galaxies.

Abstract

We present the results of our analysis of the frequencies of galaxies with tidal tails and M51-type galaxies in several deep fields of the Hubble Space Telescope (HDF-N, HDF-S, HUDF, GOODS, GEMS). In total, we have found about seven hundred interacting galaxies at redshifts z<1.5 in these fields. At z<0.7, the observed space densities of galaxies with tidal structures and M51-type galaxies have been found to increase as $\propto (1+z)^m$, where m~2.6. According to our estimates, over the last 6-7 Gyr, i.e., at z<0.7, about a third of the galaxies with M(B)<-18 mag must have undergone strong gravitational perturbations and mergers and ~1/10-1/5 of the galaxies have accreted relatively low-mass nearby satellites typical of M51-type galaxies. The possible decrease in the timescale on which a distant galaxy appears peculiar with growing z can increase considerably the estimated rate of mergers.