3 January 2018

Asger Grønnow

Most of the gas in spiral galaxies is contained in diffuse halos surrounding them. Large clouds of atomic hydrogen moving through this gas - so called High Velocity Clouds (HVCs) - are stripped of their gas as they move throudh this less dense background medium. However, they are able to travel much further before being destroyed than antcipated from fluid dynamics. In some cases they may be able to reach the disk where their gas can be accreted and take part in star formation. One possible explanation for the longevity of HVCs is that the magnetic field in the gas halo, which is usually ignored for simplicity, is reducing the gas stripping. In this talk, I will describe my work using fluid dynamics simulations with magnetic fields and show that the magnetic field can help stabilise gas clouds but not in all cases. I will alsom talk about how observations of magnetic field strengths in HCVs can be used to constrain their distances, which are otherwise often unknown, based on these simulations.