THE MOLECULAR MEDIUM OF H1413- BIMA CO(3-2) AND HCO+(4-3) OBSERVATIONS(117 )

We report observations of the CO (3-2) and HCO+ (4-3) lines toward H14 13+117, the z = 2.56 ''cloverleaf'' quasar, obtained simultaneously wi th the BIMA. These observations, with beam size 2.8 x 2.4, confirm the CO (3-2) emission redshifted to 3 mm wavelength observed at lower res olution by Barvainis and coworkers. We find an upper limit to the HCO (4-3)/CO (3-2) intensity ratio of 0.33. This suggests that the mean d ensity of the molecular gas, averaged over the beam, is lower than the 10(7) cm(-3) ''critical density'' of the HCO+ (4-3) line for collisio nal excitation. The implications of this limit depend primarily on the size scale probed by the observations. The physical conditions appear generally consistent with an average over molecular complexes in the central kiloparsecs of nearby starburst galaxies but may differ from t hose in the inner 300 pc of NGC 1068, the active nucleus with the best studied molecular medium.The technique of simultaneous line observati on at millimeter wavelengths, which minimizes relative calibration unc ertainties, is especially valuable for the broad, weak lines from high -redshift objects far which accurate absolute calibration is troubleso me. We note several diagnostic molecular line pairs, redshifted into t he 3 mm band, accessible to simultaneous measurement with the present generation of millimeter interferometers.