The HIX galaxy survey – How HI eXtreme galaxies maintain their HI reservoir

Katharina Lutz

ObAS

Stars are formed from gas, with the atomic hydrogen (HI) in galaxies being the raw fuel for the formation of giant molecular gas clouds. These clouds are the birthplaces of stars. In order to continue this star formation process in the future, galaxies need to replenish their gas reservoir. However, the total amount of gas that has been found to accrete onto local galaxies, is about one order of magnitude less than required to balance the amount of gas that is converted into stars. For my PhD thesis, I have investigated HI-rich galaxies (HIX galaxies) and the origin of their large gas content. If they are gas-rich, because they recently accreted gas, they should be perfect laboratories to study the mechanisms of gas accretion. If they are gas-rich because they are inefficient at forming stars from their given HI reservoir, then the study of these galaxies helps to understand which mechanisms regulate the galactic gas cycle. In my talk I will present a multiwavelength study of HIX galaxies and suggest a scenario explaining their massive HI discs.