The properties and environment of very young galaxies in the local Universe

In the local Universe, there are only a few dwarf star-forming galaxies with very low metal abundances, which many believe to have formed most of their stellar mass during the last few hundred Myr. But little is known of more massive Very Young Galaxies (VYGs). In this work, we study a sample of 207 VYGs that have formed at least 50% of their stellar mass within the last 1 Gyr. We find that VYGs tend to have higher surface brightness and to be more compact, dusty, asymmetric and clumpy than control sample galaxies (CSGs). A subsample with HI detections revealed that VYGs are more gas-rich than CSGs. VYGs tend to reside in the inner parts of low-mass groups and are twice as likely to be interacting with a neighbour galaxy than CSGs. On the other hand, VYGs and CSGs have similar gas metallicities and large-scale environments. Our results suggest that gas-rich interactions and mergers are the main mechanisms responsible for the recent triggering of star formation in VYGs at low redshifts.