Universität zu Köln

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

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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
Creators:	Creators Email ORCID ORCID Put Code Trevino-Morales, S. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Pilleri, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Fuente, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kramer, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Roueff, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gonzalez-Garcia, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Cernicharo, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gerin, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Goicoechea, J. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Pety, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Berne, O. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ossenkopf, V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ginard, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Garcia-Burillo, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Rizzo, J. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Viti, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED
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
Uncontrolled Keywords:	Keywords Language DENSE INTERSTELLAR CLOUDS; GRAIN SURFACE-CHEMISTRY; DEUTERIUM FRACTIONATION; LOW-TEMPERATURE; DARK CLOUDS; PHOTODISSOCIATION REGIONS; MOLECULAR-SPECTROSCOPY; EVOLUTIONARY TRACER; PHYSICAL CONDITIONS; SMALL HYDROCARBONS Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/43102