Measuring the CO/H2 ratio in shocks

\"pacs_irs_overlay\"Carbon monoxide is an easily accessible molecule used as a proxy to the content of the much abundant molecular hydrogen. In a recent study accepted for publication in Astronomy & Astrophysics, we assess the conversion ratio between CO and H2 for the first time in shocks. This was made possible by combining spectral line maps from Spitzer and Herschel space telescopes. As shown in the image on the left, the CO (orange contours, observed with Herschel) emission closely follows that  of H2 (background image, from Spitzer) and the two molecules are excited at similar temperatures.  A&A