The disk-halo connection in NGC 6946 and NGC 253
A halo of neutral hydrogen is found around an increasing number of spiral galaxies. It is not well understood how hydrogen halos are formed. The orientation of nearby spiral galaxy NGC 6946 enables us to measure vertical gas velocities in the disk of the galaxy and therefore measure how the gas gets into the halo. We find hydrogen with high velocities toward regions where stars are formed. This correlation suggests that the formation of a hydrogen halo is related to massive star formation. A similar close connection is seen in the nearby spiral galaxy NGC 253. For some hydrogen clouds in NGC 6946 we have indications that they have been accreted from outside the galaxy.
Vrijdag 26 januari 2007, 13.15 uur
promotores: Prof.dr. J.M. van der Hulst en prof.dr. R. Sancisi
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