Star formation in CALIFA survey perturbed galaxies – I. Effects of tidal interactions

Abstract

ABSTRACT We explore the effects of tidal interactions on star formation (SF) by analysing a sample of CALIFA survey galaxies. The sample consists of tidally and non-tidally perturbed galaxies whose star-forming regions are paired at the closest stellar mass surface densities, even between the same galaxy types. The regions are then compared, both on the resolved star-formation main sequence (SFMS) plane and in annular property profiles. Star-forming regions in tidally perturbed galaxies exhibit flatter SFMS slopes compared to star-forming regions in non-tidally perturbed galaxies. Despite the fact that the annular profiles show star-forming regions in tidally perturbed galaxies as being mostly older, their SF properties are never reduced against those of non-tidally perturbed galaxies. Star-forming regions in non-tidally perturbed galaxies are better candidates for SF suppression (quenching). The lowered SF with increasing stellar mass density in tidally perturbed galaxies may suggest a lower dependence of SF on stellar mass. Though the SFMS slopes, either flatter or steeper, are found independent of stellar mass density, the effect of global stellar mass cannot be ignored when distinguishing between galaxy types. Since a phenomenon or property other than local/global stellar mass may be taking part in the modulation of SF, the integrated SF properties are related to the tidal perturbation parameter. We find weak, but detectable, positive correlations for perturbed galaxies suggesting that tidal perturbations induced by close companions increase the gas accretion rates of these objects.