Life-cycle of gas in galaxies: A Local Perspective

Gas is a crucial component of galaxies, providing the fuel to form stars, and it is impossible to understand the structure and evolution of galaxies without knowing their gas properties. The coming SKA pathfinders, such as Apertif, MeerKAT, and ASKAP, will provide a wealth of information about the cold gas content of galaxies, from detailed and deep neutral hydrogen (HI) maps and a census of low HI mass systems in the nearby Universe to the global HI content of galaxies over a significant cosmic time (z>1). In order to fully utilize these data, we need to understand what the HI alone can tell us about galaxy evolution and formation and where we need further information. Two open areas of research are understanding how galaxies acquire gas to fuel their star formation, and then how that gas is converted into stars. In the nearby Universe, we have the spatial resolution to attempt to link gas (molecular and atomic) directly to sites of star formation. We also have the sensitivity to low mass and low column density gas to attempt to search directly for the accretion of gas onto galaxies. This conference aims to bring together Galactic and extragalactic astronomers who study accretion, gas and star formation to paint a complete picture of how galaxies acquire their gas, convert HI to molecular gas, and form stars. The two key topics we will address are gas accretion and star formation.

Gas Accretion: How do galaxies acquire a continuous supply of gas to fuel their star formation? Galaxies must be accreting fresh gas to sustain their current star formation rates. Understanding the origin of this gas supply is an area of active research but observing this gas directly is challenging. Around the Milky Way, individual small clouds and low column density gas can be observed but locating this gas in relation to the disk is difficult. In nearby galaxies, gas can be observed in relation to the galaxy but the observations required are very expensive. A special emphasis will be placed on presenting results from HALOGAS, an exceptionally deep HI imaging survey of nearby galaxies.

Star Formation: How is gas converted into stars? After gas is accreted, it first forms HI cloud complexes; as it becomes cooler and denser, it transitions to molecular gas. Eventually, the gas clouds become cold and dense enough to gravitationally collapse to form stars. What drives this conversion from HI to molecular gas to star formation? Spatial resolution in the nearby Universe allows us to connect observations of gas (atomic and molecular) with sites of ongoing star formation in order to determine the processes that drive star formation. In addition to discussing global star formation laws, we will also focus on regimes where these relations break down to help understand the physical processes that drive star formation. Does star formation change in the low metallicity and/or low column density regime? Can HI play a direct role in star formation? What prevents dense gas from forming stars?

More information: http://www.astron.nl/localgas2015/