Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1985
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985apj...293..522z&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 293, June 15, 1985, p. 522-529.
Astronomy and Astrophysics
Astrophysics
39
Ammonia, H Alpha Line, H Ii Regions, Interstellar Gas, Molecular Clouds, Angular Momentum, Continuous Spectra, Line Spectra, Optical Thickness, Stellar Evolution
Scientific paper
VLA observations of the ON1 region in the (J, K) = (1, 1) line of NH3 and the H76-alpha recombination line are reported. Dense and cool NH3 condensations with size scales of 0.2-0.3 pc are found near the ultracompact H II region, ON1. From the systematic shift in position with velocity, some of the condensations are interpreted as parts of a rapidly rotating structure with a large velocity gradient of 11 + or - 2 km/s/pc. This rapid rotation may be the 'spin-up' motion expected from partial conservation of the angular momentum during the collapse process. This type of rapid rotation at the 0.1 pc scale may be a key in identifying a collapsing region. The H76-alpha recombination line has a peak velocity of 5.1 + or - 2.5 km/s and is blueshifted with respect to both the NH3 emission and the OH maser emission. From the morphology, it is likely that the H II region has a peculiar velocity with respect to the neutral molecular material, while the OH masers may still be falling in toward the exciting star.
Ho Pak Tung
Reid Mark J.
Schneps Matthew H.
Zheng Xing-Wu
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