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arXiv · 1106.5464

The Herschel M33 extended survey (HerM33es): PACS spectroscopy of the star forming region BCLMP 302

B. Mookerjea·C. Kramer·C. Buchbender·M. Boquien·S. Verley·M. Relano·G. Quintana-Lacaci·S. Aalto·J. Braine·D. Calzetti·F. Combes·S. Garcia-Burillo·P. Gratier·C. Henkel·F. Israel·S. Lord·T. Nikola·M. Roellig·G. Stacey·F. S. Tabatabaei·F. van der Tak·P. van der Werf
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Abstract

Context: The emission line of [CII] at 158 micron is one of the strongest cooling lines of the interstellar medium (ISM) in galaxies. Aims: Disentangling the relative contributions of the different ISM phases to [CII] emission, is a major topic of the HerM33es program, a Herschel key project to study the ISM in the nearby spiral galaxy M33. Methods: Using PACS, we have mapped the emission of [CII] 158 micron, [OI] 63 micron, and other FIR lines in a 2'x2' region of the northern spiral arm of M33, centered on the HII region BCLMP302. At the peak of H-alpha emission, we have observed in addition a velocity resolved [CII] spectrum using HIFI. We use scatterplots to compare these data with PACS 160 micron continuum maps, and with maps of CO and HI data, at a common resolution of 12 arcsec or 50 pc. Maps of H-alpha and 24 micron emission observed with Spitzer are used to estimate the SFR. We have created maps of the [CII] and [OI] 63 micron emission and detected [NII] 122 micron and NIII 57 micron at individual positions. Results: The [CII] line observed with HIFI is significantly broader than that of CO, and slightly blue-shifted. In addition, there is little spatial correlation between [CII] observed with PACS and CO over the mapped region. There is even less spatial correlation between [CII] and the atomic gas traced by HI. Detailed comparison of the observed intensities towards the HII region with models of photo ionization and photon dominated regions, confirms that a significant fraction, 20--30%, of the observed [CII] emission stems from the ionized gas and not from the molecular cloud. The gas heating efficiency, using the ratio between [CII] and the TIR as a proxy, varies between 0.07 and 1.5%, with the largest variations found outside the HII region.

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B. Mookerjea, C. Kramer, C. Buchbender, M. Boquien, S. Verley, M. Relano, G. Quintana-Lacaci, S. Aalto, J. Braine, D. Calzetti, F. Combes, S. Garcia-Burillo, P. Gratier, C. Henkel, F. Israel, S. Lord, T. Nikola, M. Roellig, G. Stacey, F. S. Tabatabaei, F. van der Tak, P. van der Werf. 2011-06-27. The Herschel M33 extended survey (HerM33es): PACS spectroscopy of the star forming region BCLMP 302. https://doi.org/10.1051/0004-6361/201116447

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