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The Herschel M 33 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 ; Susanne Aalto (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; J. Braine ; D. Calzetti ; F. Combes ; S. Garcia-Burillo ; P. Gratier ; C. Henkel ; F. Israel ; S. Lord ; T. Nikola ; M. Rollig ; G. Stacey ; F. S. Tabatabaei ; F. van der Tak ; P. van der Werf
Astronomy & Astrophysics (0004-6361). Vol. 532 (2011), p. art. no. A152.
[Artikel, refereegranskad vetenskaplig]

Context. The emission line of [CII] at 158 mu m is one of the strongest cooling lines of the interstellar medium (ISM) in galaxies. Aims. Distinguishing the relative contributions of the different ISM phases to [CII] emission is a major objective of the HerM33es program, a Herschel key project to study the ISM in the nearby spiral galaxy M 33. Methods. Using PACS, we have mapped the emission of [CII] 158 mu m, [OI] 63 mu m, and other FIR lines in a 2' x 2' region of the northern spiral arm of M 33, centered on the HII region BCLMP302. At the peak of Ha emission, we observed in addition a velocity-resolved [CII] spectrum using HIFI. We use scatterplots to compare these data with PACS 160 mu m continuum maps, and with maps of CO and HI data, at a common resolution of 12 '' or 50 pc. Maps of Ha and 24 mu m emission observed with Spitzer are used to estimate the SFR. We created maps of the [CII] and [OI] 63 mu m emission and detected [NII] 122 mu m and [NIII] 57 mu m 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 of [CII] to the TIR as a proxy, varies between 0.07 and 1.5%, with the largest variations found outside the HII region.

Nyckelord: galaxies, M 33, photon-dominated region (PDR), HII regions, star formation, h-ii regions, far-infrared spectroscopy, long-wavelength spectrometer, photon-dominated regions, photodissociation regions, physical, conditions, m emission, interstellar-medium, nearby galaxies, m33, herm33es



Denna post skapades 2011-11-21. Senast ändrad 2014-09-02.
CPL Pubid: 148785

 

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