Mapping galaxy encounters in numerical simulations: The spatial extent of induced star formation

TL;DR

This study uses 75 galaxy merger simulations to analyze how interactions influence star formation across different regions, revealing central enhancement and outer suppression patterns that depend on galaxy mass and spin alignment.

Contribution

It provides detailed predictions on the spatial distribution of star formation during galaxy mergers, highlighting the radial dependence and independence from orbital parameters.

Findings

Star formation is enhanced in the central kiloparsec during mergers.

Outer regions show suppressed star formation beyond a few kiloparsecs.

Radial star formation patterns depend on galaxy mass and spin orientation.

Abstract

We employ a suite of 75 simulations of galaxies in idealised major mergers (stellar mass ratio ~2.5:1), with a wide range of orbital parameters, to investigate the spatial extent of interaction-induced star formation. Although the total star formation in galaxy encounters is generally elevated relative to isolated galaxies, we find that this elevation is a combination of intense enhancements within the central kpc and moderately suppressed activity at large galacto-centric radii. The radial dependence of the star formation enhancement is stronger in the less massive galaxy than in the primary, and is also more pronounced in mergers of more closely aligned disc spin orientations. Conversely, these trends are almost entirely independent of the encounter's impact parameter and orbital eccentricity. Our predictions of the radial dependence of triggered star formation, and specifically the suppression of star formation beyond kph-scales, will be testable with the next generation of integral-field spectroscopic surveys.