INTERACTION OF PROTOSTARS IN A CLOSELY-PACKED ENVIRONMENT

January 2007
It is well known that almost all stars are born in clusters, rather than in isolation, but it is not clear how protostars forming in a cluster influence to each other. Using the Berkeley-Illinois-Maryland Array (BIMA) and the Very Large Array (VLA), we carried out a detailed study of the dense gas (N2H+ and NH3) and outflow (CH3OH) emission of a cluster environment harboring very young intermediate/high-mass stars, IRAS 20293+3952, located in the Cygnus OB2 association, at 2000 parsec from the Sun. 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 figure shows in color scale the computed NH3 column density map, and in contours the CH3OH emission. NH3 (and also N2H+) reveals two clouds in the region, the main cloud in the center of the image (of 0.5 parsec and 250 Msun), and a smaller cloud to the northwest (of 0.15 parsec and 30 Msun). Within the main cloud, the NH3 column density is higher toward the south than toward the north. The figure shows the young stellar objects associated with the NH3 clouds, marked as red dots (only emitting in the millimeter -likely Class 0/I objects) and red crosses (infrared -Class II/III- objects). The high column density NH3 cores are starless core candidates, and thus this region seems to harbor young stellar objects in all evolutionary stages.

Regarding the CH3OH, we found strong emission in a fork-like structure associated with one of the four outflows of the region. Note that the outflow is deflected just when reaching the position of one of the NH3 cores. This, together with other pieces of kinematical and chemical evidence, led us to propose that the CH3OH outflow is deflected by the impact with the NH3 core, and that this could trigger the collapse in the NH3 core. In addition, we found evidences of another outflow in the region being excavating a cavity and heating its walls. Finally, the high-mass young stellar object of the region seems to be interacting with the main cloud, heating it and enhancing the emission of other molecules, like CN.

In summary, interaction between the different objects in this intermediate/high-mass star-forming region is taking place and significantly modeling the parental cloud.

This work has been published in Astronomy and Astrophysics (Volume 465, Page 219) by Aina Palau (LAEFF), Robert Estalella (UB), Josep M. Girart (IECC), Paul T. P. Ho (CfA and ASIAA), Qizhou Zhang (CfA), and Henrik Beuther (MPIA)

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