Peter Kamphuis (CASS)

Gaseous Halos of Spiral Galaxies -- Peter Kamphuis Colloquium

Marsfield Lecture Theatre

Abstract

The properties of gas in the halos of galaxies constrain global models of the interstellar medium. Studies of the extra-planar ionized hydrogen as well as the neutral hydrogen have shown that gaseous halos can improve our understanding of the disk-halo interaction, accretion from the IGM and global magnetic fields; these are key elements in galaxy evolution. Kinematical information is of particular interest since it provides clues to the origin of the gas and helps to disentangle projection effects. Such kinematical studies have shown that the rotational velocities of the gas in massive spiral galaxies decline with increasing distance to the mid-plane, the so-called
lagging halos. However, how ubiquitous such halos are, whether all gaseous halos contain such a vertical gradient in the rotational velocities as well as its origin remain open questions. Multi-wavelength studies are key in solving these problems. Currently large multi-wavelength surveys are undertaken
to obtain the properties of gaseous halos for large samples of galaxies. One of these surveys is the WSRT Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) Survey.
This survey will, for the first time, provide us with the data to correlate halo properties with global galaxy properties and provide us with a consensus of cold gas
accretion in the nearby Universe.