Star Formation in Splash Bridges

TL;DR

This paper investigates star formation in splash bridges formed from galaxy collisions, showing how collision parameters influence gravitational instability and star formation rates in the resulting gas structures.

Contribution

It introduces a model using a Jeans criterion to analyze star formation conditions in splash bridges from galaxy collisions, highlighting the effects of inclination and collision velocity.

Findings

Inclination affects starburst versus steady star formation.

Low inclination leads to starbursts, high inclination results in steady star formation.

Impact offset influences gas collision but not star formation rate.

Abstract

Splash bridges are created from the direct collision of two gas-rich disk galaxies. These direct collisions can eject gas masses on the order of \SI{e10} Msun stripped from the stellar disks of each galaxy. The Taffy Galaxy system (UGC 1294/5) is a prototypical example of a splash bridge system. CO observations of the Taffy revealed that its splash bridge contains a mass of H_2 equal to that of the Milky Way's H_2 mass. However, the little visible star formation occurring within the bridge highlights the need for models of direct gas-rich disk collisions. The Arp 194 system displays what may be another splash bridge resulting from the collision between two disk galaxies. The region between the two stellar disks contains bright clumps of active star formation. We aim to better understand the conditions for star formation in splash bridges by employing a Jeans criterion to determine where gravitational instabilities occur in the shocked and cooling gas of gas-rich disk collisions. The splash bridge results are obtained from our previous work using a sticky particle code and post-processed. We find that the inclination between the gas disks and the collision velocity with which the gas collides strongly affects the fraction of gas that will become gravitationally unstable. Low inclinations between gas disks produce starbursts whereas high inclinations result in steady-rate star formation. The offset of the gas disks at impact will determine how many gas elements directly collide but does not strongly affect the resulting star formation.