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CO rotational line emission from a dense knot in Cassiopeia A: Evidence for active post-reverse-shock chemistry

Sofia Wallström (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; C. Biscaro ; F. Salgado ; John H. Black (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; I.M. Cherchneff ; Sebastien Muller (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; O. Berné ; J. Rho ; A.G.G.M. Tiełens
Astronomy and Astrophysics (0004-6361). Vol. 558 (2013), L2,
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: ISM: supernova remnants, submillimeter: ISM, ISM: individual objects: Cassiopeia A



Denna post skapades 2013-10-08. Senast ändrad 2014-09-02.
CPL Pubid: 184903

 

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