New H i scaling relations to probe the H i content of galaxies via global H i-deficiency maps

We present new multi-wavelength scaling relations between the neutral hydrogen content (H i) and the stellar properties of nearby galaxies selected from the H i Parkes All-Sky Survey (HIPASS). We use these new scaling relations to investigate the en-vironmental dependency of the H i content of galaxies. We find that galaxies in high density environments tend to have on average less H i than galaxies with the same stellar mass in the low density environment. Our new H i scaling relations allow us to identify individual galaxies, as well as group/cluster environments, that have an ‘anomalous ’ H i content. We map the global distribution of H i-deficient and H i-excess galaxies on the sky and compare it to the large scale structure of galaxies. We find galaxy clusters to be H i-deficient, and we identify that the regions surrounding clus-ters tend to be H i-excess. Finally, we demonstrate the potential of using H i scaling relations to predict future H i surveys based on an optical redshift survey. We apply our scaling relations to 16709 galaxies in the 6dF Galaxy Survey (6dFGS) that lie in the HIPASS volume and compare our predictions to the measurements. We find that scaling relations are good method to estimate the outcome of H i surveys