The Interaction Jigsaw: investigating star formation in interacting galaxies

Abstract

Interaction between galaxies plays a pivotal role in their evolution. Ongoing star formation in spiral galaxies can be affected by these processes. Interacting galaxy pairs provide an opportunity to study these effects. We select a sample of interacting galaxies in field environments at various interaction stages and are nearly face-on and chose galaxy pairs NGC 2207/IC 2163, NGC 4017/4016 (ARP 305), and NGC 7753/7752 (ARP 86). We use the UltraViolet Imaging Telescope (UVIT) onboard AstroSat to characterize the star-forming regions in the galaxy with a superior resolution of $\mathrm{\sim 1.4\,\,\mathrm{ arcsec}}$. We identified and characterized star-forming regions in the UVIT images of the sample and correlated them with the neutral hydrogen (H i) distribution. We detected localized regions of enhancement in star formation surface density ($\mathrm{\Sigma _{SFR}}$) and distortions in the sample of galaxies. We found this consistent with the distribution of H i in the galaxy. These are possible evidence of past and ongoing interactions affecting the star formation properties in the galaxies. We then conducted a study to understand whether the observed enhancements hold true for a wider sample of interacting galaxies. We observe a moderate enhancement in the star formation rate (SFR) with the interaction class, with a maximum of 1.8 being in the merger class of galaxies. We studied the SFR enhancement for the main galaxies in our sample as a function of pair mass ratio and pair separation. We observe a strong anticorrelation between the SFR enhancement and pair mass ratio and no linear correlation between the enhancement and pair separation. This suggests that the enhancement in interaction-induced star formation may be more strongly influenced by the pair mass ratios, rather than the pair separation. We also infer that the pair separation can possibly act as a limiting parameter for the SFR enhancement.