ASTROPHYSICS 86 and 140 GHz radiocontinuum maps of the Cassiopeia A SNR

MM-wave continuum emission from the Cassiopeia A SNR was mapped at 86 and 140 GHz using an on-the-fly beam-switching technique at NRAO’s 12m telescope on Kitt Peak. Global nebular mm-wave fluxes follow quite well the Sν ∝ ν−0.77 behaviour established previously at frequencies of 1-23 GHz and vary as Sν ∝ ν−0.763±0.008 over the entire range 1-140 GHz. The 86 GHz excess found earlier by Kenney & Dent (1985) is not confirmed. As suggested by Liszt & Lucas (1995) and as shown by the transition from off-source emission to on-source absorption in the HCO+ J=1-0 line, the mm-wave radiocontinuum is too feeble to permit reliable mm-wave absorption line spectroscopy using small singledish mm-wave radiotelescopes. 12CO J=2-1 and 13CO J=1-0 emission around the nebula was mapped more fully than was previously available. There is no striking evidence which would suggest an interaction between the SNR and ambient neutral gas.