ALMA submm galaxies multi-wavelength data

A subset of 23 unlensed, bright AS2UDS SMGs have sizes measured from resolved imaging of their rest- frame far-infrared emission. We show that the extent and luminosity of the far-infrared emission are consistent with the dust emission arising from regions that are, on average, optically thick at a wavelength of {lambda}_0_>=75{mu}m (1{sigma} dispersion of 55-90{mu}m). Using the dust masses derived from our optically thick spectral energy distribution models, we determine that these galaxies have a median hydrogen column density of N_H_=9.8_-0.7_^+1.4^x10^23^cm^-2^, or a corresponding median V-band obscuration of Av=540_-40_^+80^mag, averaged along the line of sight to the source of their rest-frame ~200{mu}m emission.

We discuss the implications of this extreme attenuation by dust for the multi-wavelength study of dusty starbursts and reddening-sensitive tracers of star formation.