Star formation in Camelopardalis: Cam OB1




Lyder, David Anthony

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Star formation in the Cam OB1 region is investigated. Star formation, in general, is considered in terms of three elements: a) the structural relationship between the parent molecular clouds and newly formed stars, b) the temporal evolution of the parent molecular clouds, and c) the probability of the occurrence of star formation. Star formation in Cam OB1 over the range in l and b considered in this work, is concentrated in the vicinity of Cam R1 and appears to have led to the formation of three distinct stellar groups: a) Group I. formed ~ 1 - 50 x 106 yr ago, and located spatially and kinematically between two CO complexes, b) Group II. formed ~ 1 - 3 x 106 yr ago. and coincident with one of the previously mentioned complexes, and c) Group III. the youngest group, formed ~ I - 20 x 104 yr ago, and located at the current point of intersection between the two complexes in (a). The mass function (MF) for Groups I and II is similar to the cloud mass function of the parent molecular clouds, i.e. a power-law with exponent α ~ 2. A similar analysis for the Group III stars and associated molecular clouds cannot be performed due to the relatively small numbers in both samples. The star forming efficiency (SFE) in all cases is ~ 1%. It is proposed that cloud-cloud collisions between the CO complexes in the region triggered the formation of Groups I and III, while Group II was produced by a shock induced by the radiation pressure and stellar winds from the stars in Group I. An analysis of the molecular cloud structure in Cam OB1 and the background Perseus arm also shows that the clouds in both regions are turbulent, and typical of clouds seen elsewhere in the Galaxy. However, the clouds in Cam OB1 show a large dispersion in the degree with which they are self-gravitating, with the larger, warmer clouds being gravitationally bound. The principal data set for this work comprises fully sampled [special characters omitted] observations of the western half of Cam OB1, which were obtained at the Center for Astrophysics during the winter of 1992-1993. These data have an effective resolution of 10', a velocity resolution of 0.65 km s-1, and a sensitivity of 0.115 K. High resolution (20") observations of the [special characters omitted] transition of the most active star forming region were obtained with the James Clerk Maxwell Telescope during the winter of 1994-1995. These observations led to the discovery of a second outflow. AFGL 490 – iki, associated with IRAS 03234+5843, in the immediate vicinity of the very well-studied molecular outflow AFGL 490. Additional observations of the [special characters omitted], taken with the 26m telescope at the Dominion Radio Astrophysical Observatory during the fall of 1994, did not reveal any such masering activity in the Cam OB1 region, but did lead to the discovery of a new maser, associated with IRAS 02455+6034. in the background Perseus arm.



Stars, Evolution