On the maximal velocity of colliding galaxies

TL;DR

This paper develops a theoretical model using the Zel'dovich approximation to predict the maximum velocity of backsplash galaxies resulting from flyby events, aiding understanding of galaxy quenching.

Contribution

It introduces a novel theoretical framework to estimate the maximal velocities of backsplash galaxies in a given volume, based on galaxy collision dynamics.

Findings

Derived a formula for maximum backsplash galaxy velocity.

Validated the theory with simulation data.

Provides insights into galaxy quenching mechanisms.

Abstract

In the current galaxy formation paradigm, collisions play a crucial role. A fraction of galaxy collisions results in flyby events, and a galaxy that has passed through another galaxy is called a backsplash galaxy. Such flyby events are of particular interest for explaining the quenching of isolated galaxies. One signature of backsplash galaxies is that they have high velocities relative to their environment, since they do not move in the same flow as surrounding galaxies. This feature can be studied in simulations, but it is also useful to have a theory that can predict the velocities of backsplash galaxies. In this paper, we develop such a theory based on the Zel'dovich approximation and use it to determine the maximal expected velocity of a backsplash galaxy in a given volume.