The effect of local galaxy surface density on star formation for H i selected galaxies

Abstract

We present the result of investigations into two theories to explain the star formation rate (SFR)-density relationship. For regions of high galaxy density, either there are fewer starforming galaxies or galaxies capable of forming stars are present but some physical process is suppressing their star formation. We use Hi Parkes All-Sky Survey's (HIPASS) Hi detected galaxies and infrared and radio fluxes to investigate SFRs and efficiencies with respect to local surface density. For nearby (vel < 10000 km s-1) Hi galaxies, we find a strong correlation between H I mass and SFR. The number of H I galaxies decreases with increasing local surface density. For H I galaxies (1000 < vel < 6000 km s-1), there is no significant change in the SFR or the efficiency of star formation with respect to local surface density. We conclude that the SFR-density relation is due to a decrease in the number of H I star-forming galaxies in regions of high galaxy density and not to the suppression of star formation. © 2006 RAS.