1.3 MM EMISSION IN THE DISK OF NGC-891 - EVIDENCE OF COLD DUST

Using the IRAM 30-m telescope equipped with the MPIfR 7-channel bolome ter array, we have mapped the lambda 1.3 mm continuum emission of NGC 891, an edge-on Sb galaxy similar to the Milky Way. This emission is 7 times stronger along the major axis than the CO 2-1 line averaged ove r the 50 GHz bolometer passband, and 9 times stronger than the warm du st emission expected from the IRAS data.The lambda 1.3 mm dust emissio n correlates remarkably well. with the CO emission and poorly with HI emission, at least up to +/-7 kpc (150'') from the center. It arises m ostly from cold dust (T less than or equal to 20 K) associated with mo lecular clouds. The H-2 mass, calculated using Galactic values of the dust absorption cross section, is similar to 3 times smaller than the H-2 mass derived from the CO luminosity and Strong et al's (1988) 'sta ndard' Galactic CO to H-2 conversion factor. It is about equal to the HI mass inside a 7 kpc radius. The mass of gas associated with the col d dust is similar to 20 times the mass of gas associated with warm dus t.