Star formation in a clustered environment around the UCH region in IRAS 20293+3952

¹ Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Catalunya, Spain e-mail: apalau@am.ub.es
² Institut de Ciències de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciències, Torre C5-Parell-2a, 08193 Bellaterra, Catalunya, Spain
³ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁴ Max-Planck-Institut for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany

Received: 29 June 2006
Accepted: 8 January 2007

Abstract

Aims.We aim at studying the cluster environment surrounding the UCH region in IRAS 20293+3952, a region in the first stages of formation of a cluster around a high-mass star.

Methods.BIMA and VLA were used to observe the 3 mm continuum, N₂H⁺ (1–0), NH₃ (1, 1), NH₃ (2, 2), and CH₃OH (2–1) emission of the surroundings of the UCH region. We studied the kinematics of the region and computed the rotational temperature and column density maps by fitting the hyperfine structure of N₂H⁺ and NH₃.

Results.The dense gas traced by N₂H⁺ and NH₃ shows two different clouds, a main cloud to the east of the UCH region, of ~0.5 pc and ~250 , and a western cloud, of ~0.15 pc and ~30 . The dust emission reveals two strong components in the northern side of the main cloud, BIMA 1 and BIMA 2, associated with Young Stellar Objects (YSOs) driving molecular outflows, and two fainter components in the southern side, BIMA 3 and BIMA 4, with no signs of star forming activity. Regarding the CH₃OH, we found strong emission in a fork-like structure associated with outflow B, as well as emission associated with outflow A. The YSOs associated with the dense gas seem to have a diversity of age and properties. The rotational temperature is higher in the northern side of the main cloud, around 22 K, where there are most of the YSOs, than in the southern side, around 16 K. There is strong chemical differentiation in the region, since we determined low values of the NH₃/N₂H⁺ ratio, ~50, associated with YSOs in the north of the main cloud, and high values, up to 300, associated with cores with no detected YSOs, in the south of the main cloud. Such a chemical differentiation is likely due to abundance/depletion effects. Finally, interaction between the different sources in the region is important. First, the UCH region is interacting with the main cloud, heating it and enhancing the CN (1–0) emission. Second, outflow A seems to be excavating a cavity and heating its walls. Third, outflow B is interacting with the BIMA 4 core, likely producing the deflection of the outflow and illuminating a clump located ~0.2 pc to the northeast of the shock.

Conclusions.The star formation process in IRAS 20293+3952 is not obviously associated with interactions, but seems to take place where density is highest.