On the frequency, intensity and duration of starburst episodes triggered by galaxy interactions and mergers

TL;DR

This study analyzes how galaxy interactions and mergers influence starburst episodes, finding that such events generally cause moderate, short-lived star formation increases, with stronger bursts being rare and not significantly different at higher redshifts.

Contribution

It provides a comparative analysis of two independent simulation techniques, confirming that galaxy interactions typically trigger modest and brief starbursts across different conditions.

Findings

Strong starbursts (>5x SFR) are rare (~15%) in galaxy interactions.

Starburst durations are typically a few hundred million years.

Results are consistent across different simulation methods and models.

Abstract

We investigate the intensity enhancement and the duration of starburst episodes, triggered by major galaxy interactions and mergers. To this aim, we analyze two large statistical datasets of numerical simulations. These have been obtained using two independent and different numerical techniques to model baryonic and dark matter evolution, that are extensively compared for the first time. One is a Tree-SPH code, the other one is a grid-based N-body sticky-particles code. We show that, at low redshift, galaxy interactions and mergers in general trigger only moderate star formation enhancements. Strong starbursts where the star formation rate is increased by a factor larger than 5 are rare and found only in about 15% of major galaxy interactions and mergers. Merger-driven starbursts are also rather short-lived, with a typical duration of the activity of a few 10^8 yr. These conclusions are found to be robust, independent from the numerical techniques and star formation models. At higher redshifts where galaxies contain more gas, gas inflow-induced starbursts are neither stronger neither longer than their local counterparts. In turn, the formation of massive gas clumps, results of local Jeans instability that can occur spontaneously in gas-rich disks or be indirectly favored by galaxy interactions, could play a more important role in determining the duration and intensity of star formation episodes.