Astronomy and Astrophysics – Astrophysics
Scientific paper
May 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981a%26a....98..295p&link_type=abstract
Astronomy and Astrophysics, vol. 98, no. 2, May 1981, p. 295-299.
Astronomy and Astrophysics
Astrophysics
23
Early Stars, Formaldehyde, Molecular Clouds, Stellar Evolution, Absorption Spectra, Astronomical Maps, B Stars, Gas Dynamics, H Ii Regions, Line Spectra, O Stars
Scientific paper
The velocity structure, physical properties and evolutionary status of the H II region S 155A and the associated molecular cloud Cep B are investigated, and the relation of the cloud region to the star formation process in the Cepheus OB3 association is considered. Measurements of the 6-cm H2CO absorption line at eight positions in the ionization front of S 155 and the associated CO cloud as well as 18-cm hydrogen and carbon recombination lines in S 155 were obtained with the Effelsberg 100-m telescope. Results confirm that the H II region and the molecular cloud are in physical contact, with ionized gas flowing off the H II region at a velocity of about 11 km/sec and the ionization front moving into the molecular cloud at about 2 km/sec. The molecular cloud is found to contract with a velocity of about 2.5 km/sec, which implies a total cloud mass of 1100 solar masses and density of 1400/cu cm. Observations indicate the dominant role of the exciting star HD 217806 in cloud ionization and in the heating of IR emitting grains, as well as the existence of high-density condensations. Finally, considerations of the evolution of the younger subgroup of the Cepheus OB 3 association leads to the conclusion that the subgroup originated from the S 155A/Cep B cloud.
Panagia Nino
Thum Clemens
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