Astron. Astrophys. 347, 258-265 (1999)

5. Summary

We mapped the radiocontinuum from the Cassiopeia A SNR at and GHz at 72" and 44" resolution (HPBW, respectively) with the result that the fitted power-law slope over the range 1-140 GHz is sensibly identical to results established earlier by measurements at 1-23 GHz alone. An earlier mm-wave excess, putatively due to emission from cold dust, is not confirmed. There is no curvature to the globally averaged spectrum and no gross inhomogeneity between the shell's brighter and dimmer hemispheres.

We mapped ¹²CO J=2-1 emission and ¹³CO J=1-0 emission over a 15´ region covering the nebula to trace kinematic patterns in the molecules which might reflect a disturbance characteristic of an interaction with the expanding remnant. There is some suggestive line-widening but no conclusive evidence that the molecular and ionized gases are physically associated. Very wide CO lines and 1720 MHz OH maser emission are both absent.

We took spectra of C¹⁸O and HCO⁺ on and off the nebula, tracing the transition of the HCO⁺ from off-source emission to on-source absorption on either side of the shell. As expected from our earlier discussion in Paper I, the peak brightness at 86 GHz, 0.35 K, and the typical brightness over the nebular shell of 0.2 K, are far too small to permit reliable singledish absorption line determinations of molecular abundances.

© European Southern Observatory (ESO) 1999

Online publication: June 18, 1999
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