Molecular cloud and star formation in spiral galaxies
Clare Dobbs (University of Exeter)

I will consider how Giant Molecular Clouds (GMCs) form and evolve in spiral arms of galaxies. I will show some recent results on the lifetimes of molecular clouds and how many stars they are expected to form over their lifetimes. In particular GMCs are found to evolve on roughly the order of their crossing times, and form stars with an efficiency of a few per cent. I will also show the expected stellar age distributions in simulated GMCs, and in particular show that GMCs in inter-arm spurs are expected to contain an older stellar population than spiral arm clouds. I will then discuss the role of cloud-cloud collisions in forming GMCs, and compare with previous theories on cloud-cloud collisions. 
Finally I will show some work on simulating the Milky Way, and in particular trying to rerpoduce the Milky Way in CO. By attempting to find best fits of simulated to observed CO maps, we are able to find some constraints on the bar properties (e.g. pattern speed), number of spiral arms and the location of the observer in the Galaxy.