Dwarf-Dwarf interactions and their influence on star formation : Insights from post-merger galaxies

Abstract

Dwarf galaxies dominate the galaxy population across all redshifts, and majority of mergers are expected to occur between them. However, the impact of dwarf-dwarf mergers on star formation (SF) is less understood. In this context, we study SF in 6,155 isolated dwarf galaxies (no massive galaxy, $M_{*} > 10^{10} M_{\odot}$, within 1 Mpc$^3$), including 194 post-mergers and 5,961 non-interacting galaxies, spanning stellar masses of $10^7$ - $10^{9.6}$ M$_{\odot}$ and redshifts of 0.01 - 0.12. Post-mergers sample is from a previous study, which used deep optical images to identify dwarf galaxies with merger signatures. Using GALEX FUV data, we estimate star formation rates (SFRs) and find difference in log(SFR) between a post-merger galaxy and the median of its corresponding control sample, matched in stellar mass and redshift. SFR offsets range from -2 to +2 dex, indicating both enhancement and suppression of SF in our sample with 67% of post-mergers showing enhancement. The median SFR is found to be elevated by 0.24 dex ($\sim$1.73 times) in post-mergers, comparable to enhancements seen in massive galaxies. SF is found to be similarly enhanced in both the central (6" diameter region) and outer regions of post-mergers with respect to their non-interacting counterparts. This is in contrast to what is observed in massive galaxies, where the merger-triggered SF is more significant in the central regions. In the given small range of redshift, post-merger dwarfs exhibit a higher median specific SFR compared to their non-interacting counterparts. About 33% of post-mergers are quenched, possibly reflecting a later stage of the post-merger regime, where quenching can happen as observed in massive galaxies. This study suggests that dwarf-dwarf mergers can affect SF in the local universe. A more comprehensive study of post-merger dwarfs is required to understand their evolution.