CO rotational line emission from a dense knot in Cassiopeia A: Evidence for active post-reverse-shock chemistry
Journal article, 2013
We report a Herschel detection of high-J rotational CO lines from a dense knot in the supernova remnant Cas A. Based on a combined analysis of these rotational lines and previously observed ro-vibrational CO lines, we find the gas to be warm (two components at ~400 and 2000 K) and dense (1e6−7 cm-3), with a CO column density of ~5e17 cm-2. This, along with the broad line widths (~400 km/s), suggests that the CO emission originates in the post-shock region of the reverse shock. As the passage of the reverse shock dissociates any existing molecules, the CO has most likely reformed in the past several years in the post-shock gas. The CO cooling time is similar to the CO formation time, therefore we discuss possible heating sources (UV photons from the shock front, X-rays, electron conduction) that may maintain the high column density of warm CO.
ISM: individual objects: Cassiopeia A
ISM: supernova remnants
submillimeter: ISM
Author
Sofia Wallström
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
C. Biscaro
Universitat Basel
F. Salgado
Leiden Observatory Research Institute
John H Black
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
I.M. Cherchneff
Universitat Basel
Sebastien Muller
Chalmers, Earth and Space Sciences, Onsala Space Observatory
O. Berné
CNRS Centre National de la Recherche Scientifique
Universite de Toulouse
J. Rho
NASA Ames Research Center
SETI Institute
Aggm Tielens
Leiden Observatory Research Institute
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 558 L2 L2Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
Infrastructure
Onsala Space Observatory
DOI
10.1051/0004-6361/201322576