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Wednesday 14 Jan 2015Seminar: Simulating Observational Star Formation **4pm**

Dr Paul Clark - Cardiff University

Physics, 4th floor 16:00-17:00

We will review the role that molecules play in the star formation process, both as a coolant of the interstellar medium, and as a tracer of the star-forming gas. This talk focuses on the results of numerical models that can simultaneously capture the chemistry of the ISM and the star formation that occurs in molecular clouds. We will discuss why CO is such a good tracer of star formation, even though the cooling provided by the molecule is not needed for star formation to occur, and investigate the chemistry and thermodynamics of molecular clouds as we move to low metallicity environments. We will also show how the delay between the onset of H2 formation and CO appears to roughly constant, at around 2 Myr, suggesting that the formation of molecular clouds — as they are observationally defined — is a fairly rapid process. We will also take a look at how the X-factor (the conversion factor between integrated CO emission and H2 column density) may vary with cloud environment. Finally, we will present results from models of the chemistry and thermodynamics of the Galactic Centre (GC) cloud commonly known as “The Brick” (or “Lima Bean”). We find that the both the interstellar radiation field and cosmic-ray ionisation rates in the GC need to be roughly 1000 times the local values if we are to reproduce the gas and and dust temperatures that are observed for this object. We also predict that clouds in the GC environment cool mainly via OI emission, rather than the standard CO/C+ emission that is common for Milky Way clouds.

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