“The many facets of interaction-induced star-formation in galaxies”
What is the spectrum of possible outcomes when galaxies merge? How often, and on which time scales, can this lead to accelerated vs. slowing growth?
A key step towards understanding different evolutionary pathways is to quantify how gas fractions and star-formation efficiency evolve during galaxy interactions. In this presentation I’ll describe a meta-analysis we conducted with this aim on several samples of interacting or starbursting SDSS galaxies, exploiting IRAM 30 m CO spectroscopy. We find that molecular gas reservoirs are boosted throughout most stages of galaxy interactions, plausibly due to torque-driven inflows of halo gas and gas compression. The gas fraction and depletion time offsets of mergers and post-starbursts anti-correlate with their distance from the galaxy main sequence d(MS), evidencing the role of star-formation efficiency (SFE) in driving the strongest starburst events. Our multi-sample analysis paints a coherent picture of the starburst-merger connection throughout the low-z merger sequence. It reconciles contradictory literature findings by highlighting that gas fraction enhancements and SFE variations both play their part in merger-driven star formation.
Interaction-driven star formation can be heavily dust-obscured, making radio continuum emission an esp. valuable star-formation rate (SFR) tracer in such circumstances. Time permitting, I will briefly outline a novel approach for calibrating radio-based SFRs – from low to high redshift – based on empirical modelling of radio luminosity function evolution.