Volume 563, March 2014
|Number of page(s)||22|
|Section||Interstellar and circumstellar matter|
|Published online||03 March 2014|
Max-Planck-Institut für Radioastronomie,
auf dem Hügel 69, 53121
2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MA 02140 Cambridge, USA
Received: 19 April 2013
Accepted: 4 January 2014
We present deep Very Large Array H66α radio recombination line (RRL) observations of the two cometary H ii regions in DR 21. With these sensitive data, we test the “hybrid” bow shock/champagne flow model previously proposed for the DR 21 H ii regions. The ionized gas down the tail of the southern H ii region is redshifted by up to ~30 km s-1 with respect to the ambient molecular gas, as expected in the hybrid scenario. The RRL velocity structure, however, reveals the presence of two velocity components in both the northern and southern H ii regions. This suggests that the ionized gas is flowing along cone-like shells, swept-up by stellar winds. The observed velocity structure of the well-resolved southern H ii region is most consistent with a picture that combines a stellar wind with stellar motion (as in bow shock models) along a density gradient (as in champagne flow models). The direction of the implied density gradient is consistent with that suggested by maps of dust continuum and molecular line emission in the DR 21 region.
Key words: HII regions / stars: formation / ISM: individual objects: DR21 / ISM: kinematics and dynamics / radio lines: ISM
The image cubes are only available as a FITS file at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/A39
Table 2, Fig. 4, and Appendices A and B are available in electronic form at http://www.aanda.org
Member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne.
© ESO, 2014
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