An Upper Limit to the Molecular Density in IC 342

Extract

A search for CS J=7−6 emission from the core of the galaxy IC342 was undertaken with the Caltech Submillimeter Observatory. At the line frequency of 342.883 GHz, the beamsize is 20″. An upper limit to T_MBΔv of 0.4 K km s⁻¹ was obtained. This upper limit can be compared directly to the CS J=3−2 integrated line flux (3.1 K km s⁻¹; Mauersberger and Henkel 1989), because the beam used for that observation was similar (17″). The J=7−6 to J=3−2 line ratio limit is 0.13 with no correction for the slight difference in beamsize, and ≈ 0.15 with this correction included. Assuming T_kin = 70 K (Martin and Ho 1986), this leads to a density upper limit of about 5 × 10⁵ cm⁻³ for this gas.