A molecular line survey of Sagittarius B2 and Orion-KL from 70 to 115 GHz. II - Analysis of the data.

Over 800 lines in OMC-1 and over 700 in Sgr B2 were observed in the NRAO 3-mm survey. Detailed LTE analysis of 33 species has been performed using numbers of transitions in the range 4-98. Limitations of the LTE optically thin approach are emphasized, in particular its failure to account for the anomalously strong emission from intrisically weak transitions in all the most complex species including CH3OHCO, (CH3)2O, CH3CHO, EtOH, NH2CHO, CH2CHCN, and EtCN. A detailed radiative-transfer analysis of all species with a sufficient number of transitions was also performed. The intensity and abundance ratios of the existing 3-mm surveys of Sgr B2 (NRAO, BTL) and OMC-1 (NRAO, Onsala) are compared to deduce the relative contributions to the emission of each molecular species from compact hot sources and from extended cool regions. It is concluded that the chemistries of the two regions are similar, which suggests a similar cosmic-ray flux, evolutionary stage, and elemental abundance distribution.