by Steven Janowiecki (ICRAR/UWA)

Abstract. I will talk about recent work studying gas and star-formation in samples of galaxies. In particular, using the new xGASS survey, we have found unusually gas-rich and star-forming central galaxies in small groups, which we interpret as evidence of feeding from the cosmic web. At the other extreme, the ALFALFA HI survey is finding gas-rich galaxies with almost invisible stellar populations. These (almost) dark galaxies are exceptionally inefficient at forming stars and may be related to the recently re-discovered class of “ultra-diffuse” galaxies.