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.

submillimeter: ISM

ISM: supernova remnants

ISM: individual objects: Cassiopeia A


Sofia Wallström

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

C. Biscaro

University of Basel

F. Salgado

Leiden University

John H Black

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

I.M. Cherchneff

University of Basel

Sebastien Muller

Chalmers, Earth and Space Sciences, Onsala Space Observatory

O. Berné

Centre national de la recherche scientifique (CNRS)

University of Toulouse

J. Rho

NASA Ames Research Center

SETI Institute

Aggm Tielens

Leiden University

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 558 L2 L2

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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