Molecular gas toward supernova remnant Cassiopeia A

Abstract

We mapped 12CO J=1-0, 12CO J=2-1, 13CO J=1-0, and 13CO J=2-1 lines toward supernova remnant (SNR) Cassiopeia A with the IRAM 30m telescope. The molecular clouds (MCs) along the line of sight of Cas A do not show optically thin, shock-broadened 12CO lines ($\Delta V\le 7$ km s${}^{-1}$ toward Cas A), or high-temperature features from shock heating ($T_k\le 22$ K toward Cas A). Therefore, we suggest that there is no physical evidence to support that the SNR is impacting the molecular gas. All the detected MCs are likely in front of Cas A, as implied by the HCO+ absorption line detected in the same velocity ranges. These MCs contribute H${}_2$ column densities of $5\times 10^{21}$ cm${}^{-2}$, $5\times 10^{21}$ cm${}^{-2}$, and $2\times 10^{21}$ cm${}^{-2}$ in the west, south, and center of the SNR, respectively. The 20 K warm gas at $V_{LSR}\sim -47$ km s${}^{-1}$ is distributed along a large-scale molecular ridge in the south of Cas A. Part of the gas is projected onto Cas A, providing a foreground H${}_2$ mass of $\sim 200(d/3kpc{)}^2$ Msun, consistent with the mass of cold dust (15--20 K; 2--4 Msun) found in front of the SNR. We suggest that the 20 K warm gas is heated by background cosmic rays with an ionization rate of $\zeta ({\mathrm{H}}_2)\sim 2\times 10^{-16}$ s${}^{-1}$. The cosmic rays or X-ray emission from Cas A are excluded as the heating sources of the clouds.

18 pages, 8 figures, 2 tables; Accepted to ApJ

References in corpus (16)

• The Cassiopeia A Supernova was of Type IIB
• The Expansion Asymmetry and Age of the Cassiopeia A Supernova Remnant
• The cosmic ray ionization rate in the Galactic disk, as determined from observations of molecular ions
• The dust mass in Cassiopeia A from a spatially resolved Herschel analysis
• FellWalker - a Clump Identification Algorithm
• A cut-off in the TeV gamma-ray spectrum of the SNR Cassiopeia A
• No cold dust within the supernova remnant Cassiopeia A
• Cosmic ray induced ionisation of a molecular cloud shocked by the W28 supernova remnant
• Carbon and hydrogen radio recombination lines from the cold clouds towards Cassiopeia A
• Carbon Monoxide in the Cassiopeia A Supernova Remnant
• Multi-wavelength study of the supernova remnant Kes 79 (G33.6+0.1): On its supernova properties and expansion into a molecular environment
• LOFAR observations of decameter carbon radio recombination lines towards Cassiopeia A
• Interaction between Cassiopeia A and Nearby Molecular Clouds
• Mapping low frequency carbon radio recombination lines towards Cassiopeia A at 340, 148, 54 and 43 MHz
• High spatial resolution X-ray spectroscopy of SNR Cassiopeia A with {\sl Chandra}
• [CI] 492 GHz mapping toward Cas A

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• A Small-Scale Investigation of Molecular Emission toward the Tip of the Western Lobe of W50/SS433
• A Large-field J=1-0 Survey of CO and Its Isotopologues Toward the Cassiopeia A Supernova Remnant
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• Molecular Gas of the Most Massive Spiral Galaxies I: a Case Study of NGC 5908
• Critical comments on publications by S. Hoffmann and N. Vogt on historical novae/supernovae and their candidates
• A High Resolution Study of Carbon Radio Recombination Lines towards Cassiopeia A
• Near-Infrared Spectroscopy of Dense Ejecta Knots in the Outer Eastern Area of the Cassiopeia A Supernova Remnant
• Optical observations of the Galactic SNR HB9 and H II region G159.2+3.3
• Observations of Carbon Radio Recombination Lines with the NenuFAR telescope. I. Cassiopeia A and Cygnus A
• The forward and reverse shock dynamics of Cassiopeia A