Astronomy and Astrophysics, volume 465, 219-233 (2007/4-1)
Star formation in a clustered environment around the UCHII region in IRAS 20293+3952.
PALAU A., ESTALELLA R., GIRART J.M., HO P.T.P., ZHANG Q. and BEUTHER H.
Abstract (from CDS):
We aim at studying the cluster environment surrounding the UCHII region in IRAS 20293+3952, a region in the first stages of formation of a cluster around a high-mass star.BIMA and VLA were used to observe the 3mm continuum, N2H+(1-0), NH3(1, 1), NH3(2, 2), and CH3OH(2-1) emission of the surroundings of the UCHII 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.The dense gas traced by N2H+ and NH3 shows two different clouds, a main cloud to the east of the UCHII region, of ∼0.5pc and ∼250M☉, and a western cloud, of ∼0.15pc and ∼30M☉. 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 22K, where there are most of the YSOs, than in the southern side, around 16K. 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 UCHII 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 ∼0.2pc to the northeast of the shock.The star formation process in IRAS 20293+3952 is not obviously associated with interactions, but seems to take place where density is highest.
stars: formation - ISM: individual objects: IRAS 20293+3952 - dust, extinction - ISM: clouds
Fig.1, Table 4: [KBD2002] IRAS 20293+3952 IRS N (Nos 3-6) added. Fig.1, Tables 2, 4: [PEG2007] BIMA N (Nos 1-4), [PEG2007] UCHII N=1, [PEG2007] WWS (Nos NWS, SWS), [PEG2007] WCloud N=1.
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