Trevino-Morales, S. P., Pilleri, P., Fuente, A., Kramer, C., Roueff, E., Gonzalez-Garcia, M., Cernicharo, J., Gerin, M., Goicoechea, J. R., Pety, J., Berne, O., Ossenkopf, V., Ginard, D., Garcia-Burillo, S., Rizzo, J. R. and Viti, S. (2014). Deuteration around the ultracompact HII region Monoceros R2. Astron. Astrophys., 569. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746
Full text not available from this repository.Abstract
Context. The massive star-forming region Monoceros R2 (Mon R2) hosts the closest ultra-compact HII region, where the photon-dominated region (PDR) between the ionized and molecular gas can be spatially resolved with current single-dish telescopes. Aims. We aim at studying the chemistry of deuterated molecules toward Mon R2 to determine the deuterium fractions around a high-UV irradiated PDR and investigate the chemistry of these species. Methods. We used the IRAM-30 m telescope to carry out an unbiased spectral survey toward two important positions (namely IF and MP2) in Mon R2 at 1, 2, and 3 mm. This spectral survey is the observational basis of our study of the deuteration in this massive star-forming region. Our high spectral resolution observations (similar to 0.25-0.65 km s(-1)) allowed us to resolve the line profiles of the different species detected. Results. We found a rich chemistry of deuterated species at both positions of Mon R2, with detections of C2D, DCN, DNC, DCO+, D2CO, HDCO, NH2D, and N2D+ and their corresponding hydrogenated species and rarer isotopologs. The high spectral resolution of our observations allowed us to resolve three velocity components: the component at 10 km s(-1) is detected at both positions and seems associated with the layer most exposed to the UV radiation from IRS 1; the component at 12 km s(-1) is found toward the IF position and seems related to the foreground molecular gas; finally, a component at 8.5 km s(-1) is only detected toward the MP2 position, most likely related to a low-UV irradiated PDR. We derived the column density of the deuterated species (together with their hydrogenated counterparts), and determined the deuterium fractions as D-frac = [XD]/[XH]. The values of Dfrac are around 0.01 for all the observed species, except for HCO+ and N2H+, which have values 10 times lower. The values found in Mon R2 are similar to those measured in the Orion Bar, and are well explained with a pseudo-time-dependent gas-phase model in which deuteration occurs mainly via ion-molecule reactions with H2D+, CH2D+ and C2HD+. Finally, the [(HCN)-C-13]/[(HNC)-C-13] ratio is very high (similar to 11) for the 10 km s(-1) component, which also agree with our model predictions for an age of similar to 0.01 to a few 0.1 Myr. Conclusions. The deuterium chemistry is a good tool for studying the low-mass and high-mass star-forming regions. However, while low-mass star-forming regions seem well characterized with D-frac(N2H+) or D-frac(HCO+), a more complete chemical modeling is required to date massive star-forming regions. This is due to the higher gas temperature together with the rapid evolution of massive protostars.
Item Type: | Journal Article | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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URN: | urn:nbn:de:hbz:38-431025 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DOI: | 10.1051/0004-6361/201423407 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Journal or Publication Title: | Astron. Astrophys. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Volume: | 569 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Date: | 2014 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Publisher: | EDP SCIENCES S A | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Place of Publication: | LES ULIS CEDEX A | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
ISSN: | 1432-0746 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Language: | English | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Faculty: | Unspecified | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Divisions: | Unspecified | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Subjects: | no entry | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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URI: | http://kups.ub.uni-koeln.de/id/eprint/43102 |
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