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- Mookerjea, B., et al.
(författare)
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The Herschel M 33 extended survey (HerM33es): PACS spectroscopy of the star-forming region BCLMP 302
- 2011
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 532, s. art. no. A152-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Persson, Carina, 1964, et al.
(författare)
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Nitrogen hydrides in interstellar gas towards G10.6-0.4 (W31C) and W49N
- 2011
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Ingår i: IAU Symposium 280, Poster 76, Session 2, The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Toledo, Spain, May 30-June 3, 2011, #296. ; 280:76
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The PRISMAS key programme has used the HIFI instrument on board Herschel to observe interstellar nitrogen hydrides along the sight-lines towards G10.6-0.4 (W31C) and W49N in order to elucidate the production pathways leading to nitrogen bearing species. We report observations of the NH N=1-0, J=2-1 and J=1-0, ortho-NH2 111-000, ortho-NH3 10-00 and 20-10, para-NH3 21-11 transitions, and unsuccessful searches for NH+ in both sources. All detections show emission and absorption associated directly with the hot-core source itself as well as absorption by foreground material over a wide range of velocities. The NH, NH2 and NH3 spectra show strikingly similar and non-saturated absorption features, which we attribute to diffuse molecular gas. The similarity of the profiles suggest fairly uniform abundances relative to hydrogen. The derived relative and absolute abundances are discussed with reference to models of gas-phase and surface chemistry.
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