Universität zu Köln

Mookerjea, B., Vastel, C., Hassel, G. E., Gerin, M., Pety, J., Goldsmith, P. F., Black, J. H., Giesen, T., Harrison, T., Persson, C. M. and Stutzki, J. (2014). Detection of a dense clump in a filament interacting with W51e2. Astron. Astrophys., 566. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

Full text not available from this repository.

Abstract

In the framework of the Herschel/PRISMAS guaranteed time key program, the line of sight to the distant ultracompact H II region W51e2 has been observed using several selected molecular species. Most of the detected absorption features are not associated with the background high-mass star-forming region and probe the diffuse matter along the line of sight. We present here the detection of an additional narrow absorption feature at similar to 70 km s(-1) in the observed spectra of HDO, NH3 and C-3. The 70 km s(-1) feature is not uniquely identifiable with the dynamic components (the main cloud and the large-scale foreground filament) so-far identified toward this region. The narrow absorption feature is similar to the one found toward low-mass protostars, which is characteristic of the presence of a cold external envelope. The far-infrared spectroscopic data were combined with existing ground-based observations of (CO)-C-12, (CO)-C-13, CCH, CN, and C3H2 to characterize the 70 km s(-1) component. Using a non-LTE analysis of multiple transitions of NH3 and CN, we estimated the density (n(H-2) similar to (1-5) x 10(5) cm(-3)) and temperature (10-30 K) for this narrow feature. We used a gas-grain warm-up based chemical model with physical parameters derived from the NH3 data to explain the observed abundances of the different chemical species. We propose that the 70 km s(-1) narrow feature arises in a dense and cold clump that probably undergoes collapse to form a low-mass protostar, formed on the trailing side of the high-velocity filament, which is thought to be interacting with the W51 main cloud. While the fortuitous coincidence of the dense clump along the line of sight with the continuum-bright W51e2 compact HII region has contributed to its nondetection in the continuum images, this same attribute makes it an appropriate source for absorption studies and in particular for ice studies of star-forming regions.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Mookerjea, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Vastel, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hassel, G. E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gerin, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Pety, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Goldsmith, P. F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Black, J. H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Giesen, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Harrison, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Persson, C. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stutzki, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-436458
DOI:	10.1051/0004-6361/201323131
Journal or Publication Title:	Astron. Astrophys.
Volume:	566
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 HERSCHEL/HIFI OBSERVATIONS; NITROGEN HYDRIDES; DEUTERATED WATER; GAS-PHASE; DEUTERIUM FRACTIONATION; RADIO-CONTINUUM; ORION KL; CLOUDS; LINE; CHEMISTRY Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/43645