1.3MM CONTINUUM EMISSION IN THE LATE-TYPE SPIRAL NGC-4631 - DUST IN NGC-4631

We have used the IRAM 30meter telescope with the MPlfR 7-channel bolom eter to map the lambda1.3mm continuum emission from the central 4' x 3 ' region of the edge-on spiral NGC 4631. About 6/7 of the flux is due to thermal radiation from cool dust and its distribution has been comp ared with recent HI and CO maps at similar angular resolution. The rem aining 15% is due to the 12CO (2-1) line (approximately 11%), the 13CO (2-1) line (approximately 1%), and synchrotron and free-free emission . Both the CO and 1.3mm continuum are concentrated in the inner approx imately 2kpc and have a similar morphology whereas the HI emission is much more extended. To within observational uncertainties, however, th e dust emission per gram of interstellar matter is similar in the atom ic and molecular components after making the usual assumptions to conv ert HI and CO line fluxes to HI and H2 column densities. The fact that the gas mass calculated from the thermal dust emission is equal to or slightly higher than the mass from the HI and CO lines suggests that in NGC 4631 the N(H2)/I(CO)(1-0) ratio is not overestimated.