Ossenkopf, V., Koumpia, E., Okada, Y., Mookerjea, B., van der Tak, F. F. S., Simon, R., Puetz, P. and Guesten, R. (2015). Fine-structure line deficit in S 140. Astron. Astrophys., 580. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Aims. We try to understand the gas heating and cooling in the S 140 star-forming region by spatially and spectrally resolving the distribution of the main cooling lines with GREAT/SOFIA and combining our data with existing ground-based and Herschel observations that trace the energy input and the density and temperature structure of the source. Methods. We mapped the fine-structure lines of [Oi] (63 mu m) and [Cii] (158 mu m) and the rotational transitions of CO 13-12 and 16-15 with GREAT/SOFIA and analyzed the spatial and velocity structure to assign the emission to individual heating sources. We measure the optical depth of the [Cii] line and perform radiative transfer computations for all observed transitions. By comparing the line intensities with the far-infrared continuum we can assess the total cooling budget and measure the gas heating efficiency. Results. The main emission of fine-structure lines in S 140 stems from a 8.3 '' region close to the infrared source IRS 2 that is not prominent at any other wavelength. It can be explained by a photon-dominated region (PDR) structure around the embedded cluster if we assume that the [Oi] line intensity is reduced by a factor of seven owing to self-absorption. The external cloud interface forms a second PDR at an inclination of 80-85 degrees illuminated by a UV field of 60 times the standard interstellar radiation field. The main radiation source in the cloud, IRS 1, is not prominent at all in the fine-structure lines. We measure line-to-continuum cooling ratios below 10-4, i.e. values lower than in any other Galactic source, actually matching the far-IR line deficit seen in ULIRGs. In particular, the low intensity of the [Cii] line can only be modeled by an extreme excitation gradient in the gas around IRS 1. We found no explanation for why IRS 1 shows no associated fine-structure line peak, while IRS 2 does. Conclusions. The inner part of S 140 mimics the far-IR line deficit in ULIRGs thereby providing a template that may lead to a future model.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Ossenkopf, V.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Koumpia, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Okada, Y.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Mookerjea, B.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
van der Tak, F. F. S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Simon, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Puetz, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Guesten, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-397193
DOI: 10.1051/0004-6361/201526231
Journal or Publication Title: Astron. Astrophys.
Volume: 580
Date: 2015
Publisher: EDP SCIENCES S A
Place of Publication: LES ULIS CEDEX A
ISSN: 1432-0746
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
PHOTON-DOMINATED REGIONS; POLYCYCLIC AROMATIC-HYDROCARBONS; FAR-INFRARED SPECTROSCOPY; C-12/C-13 ISOTOPE RATIO; STAR-FORMING REGIONS; C-II; PHYSICAL CONDITIONS; INTERSTELLAR-MEDIUM; PHOTODISSOCIATION REGIONS; MOLECULAR CLOUDSMultiple languages
Astronomy & AstrophysicsMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/39719

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