Do minor interactions trigger star formation in galaxy pairs?

TL;DR

This study investigates how minor galaxy interactions influence star formation and quenching, revealing that most minor pairs are quiescent and that environmental factors and galaxy features like bulges or bars are not primary quenching drivers.

Contribution

The paper provides the first detailed analysis of minor interactions' effects on star formation and quenching in galaxy pairs, using SDSS data and control samples.

Findings

Minor galaxy pairs show significant differences in SFR and colour compared to isolated controls.

Quenching in minor pairs decreases with increasing separation, plateauing beyond 50 kpc.

Most minor pairs are quiescent, with minimal influence from bulges, bars, or AGN activity.

Abstract

We analyze the galaxy pairs in a set of volume limited samples from the SDSS to study the effects of minor interactions on the star formation rate (SFR) and colour of galaxies. We carefully design control samples of the isolated galaxies by matching the stellar mass and redshift of the minor pairs. The SFR distributions and colour distributions in the minor pairs differ from their controls at $>99\%$ significance level. We also simultaneously match the control galaxies in stellar mass, redshift and local density to assess the role of the environment. The null hypothesis can be rejected at $>99\%$ confidence level even after matching the environment. Our analysis shows a quenching in the minor pairs where the degree of quenching decreases with the increasing pair separation and plateaus beyond 50 kpc. We also prepare a sample of minor pairs with $H_{\alpha}$ line information. We calculate the SFR of these galaxies using the $H_{\alpha}$ line and repeat our analysis. We observe a quenching in the $H_{\alpha}$ sample too. We find that the majority of the minor pairs are quiescent systems that could be quenched due to minor interactions. Combining data from the Galaxy Zoo and Galaxy Zoo2, we find that only $\sim 1\%$ galaxies have a dominant bulge, $4\%-7\%$ galaxies host a bar, and $5\%-10\%$ galaxies show the AGN activity in minor pairs. This indicates that the presence of bulge, bar and AGN activity plays an insignificant role in quenching the galaxies in minor pairs. The more massive companion satisfies the criteria for mass quenching in most of the minor pairs. We propose that the stripping and starvation likely caused the quenching in the less massive companion at a later stage of evolution.