Title: CH 3 GHz Observations of the Galactic Center
Abstract: A 3 × 3 map of the Galactic center was made at 9' resolution and 10' spacing in the CH 2Π1/2, J = 1/2, F = 1-1 transition at 3335 MHz. The CH emission shows a velocity extent that is close to that of the CO(1-0) line, but the CH line profiles differ markedly from the CO. The 3335 MHz CH transition primarily traces low-density molecular gas in the high-density, high-pressure environment of the Galactic center interstellar medium. If the empirical N(CH)-N(H2) relation derived for molecular clouds in the disk is valid at the Galactic center, then our observations indicate that the mass of the low-density component within ~30 pc of the Galactic center is ~9 × 106 M☉. The CO-H2 conversion factor obtained for the low-density gas in the mapped region is greater than that thought to apply to the dense molecular gas at the Galactic center. The CH spectra show evidence of emission from molecular clouds along the line of sight in both the foreground and the background. The scale height of these clouds ranges from 27 to 109 pc, consistent with previous work based on observations of molecular clouds in the inner Galaxy.