Dust around H II regions: Pt. 2

Submillimetre continuum maps, and IRAS calibrated raw data maps, on which a new 'destriping' technique has been used, are presented of W49A, showing extensive emission from cool dust in the region. The dust emission is fitted by a greybody function. The cloud is shown to be optically thin at wavelengths longer than 150 μm, so the submillimetre fluxes can be used to estimate the total dust mass, which is found to be 2400 M solar masses. The 'filling factor' implies that the dust cloud is highly fragmented on small scales. The total far-infrared luminosity of the cloud is found to be 2.7 x 107 L times the solar luminosity. The morphology of the cloud is diagnosed as consisting of an association of H II regions surrounded by a dust cloud composed of grains at two characteristic temperatures. (author)