Submillimeter Continuum Properties of Cold Dust in the Inner Disk and Outflows of M82

Abstract

Deep submillimeter (submm) continuum imaging observations of the starburst galaxy M82 are presented at 350, 450, 750 and 850 micron wavelengths, that were undertaken with the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope in Hawaii. The presented maps include a co-addition of submm data mined from the SCUBA Data Archive. The co-added data produce the deepest submm continuum maps yet of M82, in which low-level 850 micron continuum has been detected out to 1.5kpc, at least 10% farther in radius than any previously published submm detections of this galaxy. The overall submm morphology and spatial spectral energy distribution of M82 have a general north-south asymmetry consistent with H-alpha and X-ray winds, supporting the association of the extended continuum with outflows of dust grains from the disk into the halo. The new data raise interesting points about the origin and structure of the submm emission in the inner disk of M82. In particular, SCUBA short wavelength evidence of submm continuum peaks that are asymmetrically distributed along the galactic disk suggests the inner-disk emission is re-radiation from dust concentrations along a bar (or perhaps a spiral) rather than edges of a dust torus, as is commonly assumed. Higher resolution submm interferometery data from the Smithsonian Submillimeter Array and later Atacama Large Millimeter Array should spatially resolve and further constrain the reported dust emission structures in M82.