University of Heidelberg

Talk Details

Monday, July 14, 2014 - 11:00am

László Szűcs (ZAH/ITA):

"Chemistry of CO in molecular clouds"

Abstract. The carbon monoxide molecule (CO) and its isotopes are the most widely used gas phase tracers of total column density and mass in studies of the interstellar medium. CO isotopes are relatively easily detectable due to their high abundances and low-lying rotational transitions, which are excited at typical molecular cloud densities and temperatures. CO isotopes, however, in not all circumstances are good tracers of the total column density and cloud mass. Sub-thermal excitation, optical depth effects and over-simplified assumptions in the emission-to-column density conversion methods might result in an overestimated column density at certain integrated line intensity ranges and in an underestimated total cloud mass. In this talk, I review the chemistry and excitation of CO in molecular clouds and describe the most frequently used methods for deriving column densities from CO emission. Then, I benchmark these methods based on realistic cloud simulations (i.e. turbulent cloud with self-consistent heating/cooling and chemistry) and suggest improvements.

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