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Infall through the evolution of high-mass star-forming clumps

  • With the GREAT receiver at the Stratospheric Observatory for Infrared Astronomy (SOFIA), nine massive molecular clumps have been observed in the ammonia 32+−22− line at 1.8 THz in a search for signatures of infall. The sources were selected from the ATLASGAL submillimeter dust continuum survey of our Galaxy. Clumps with high masses covering a range of evolutionary stages based on their infrared properties were chosen. The ammonia line was detected in all sources, leading to five new detections and one confirmation of a previous detection of redshifted absorption in front of their strong THz continuum as a probe of infall in the clumps. These detections include two clumps embedded in infrared dark clouds. The measured velocity shifts of the absorptions compared to optically thin C17O (3–2) emission are 0.3–2.8 km s-1, corresponding to fractions of 3% to 30% of the free-fall velocities of the clumps. The ammonia infall signature is compared with complementary data of different transitions of HCN, HNC, CS, and HCO+, which are often used to probe infall because of their blue-skewed line profiles. The best agreement with the ammonia results is found for the HCO+ (4–3) transitions, but the latter is still strongly blended with emission from associated outflows. This outflow signature is far less prominent in the THz ammonia lines, which confirms it as a powerful probe of infall in molecular clumps. Infall rates in the range from 0.3 to 16 × 10-3 M⊙/yr were derived with a tentative correlation with the virial parameters of the clumps. The new observations show that infall on clump scales is ubiquitous through a wide range of evolutionary stages, from L/M covering about ten to several hundreds.

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Document Type:Article
Parent Title (English):A&A (Astronomy & Astrophysics)
First Page:A149
ArXiv Id:http://arxiv.org/abs/1510.08374
Publisher:EDP Sciences
Date of first publication:2016/01/13
Tag:ISM: kinematics and dynamics; ISM: molecules; stars: formation
Departments, institutes and facilities:Fachbereich Elektrotechnik, Maschinenbau, Technikjournalismus
Dewey Decimal Classification (DDC):5 Naturwissenschaften und Mathematik / 52 Astronomie / 520 Astronomie und zugeordnete Wissenschaften
Entry in this database:2016/03/10