Sub-millimeter galaxies (SMGs) are typically high-redshift galaxies at 2<z<3 with large infrared luminosities powered by intense star formation, and have been suggested as the most likely progenitor of local massive elliptical galaxies. However, up until recent interferometric observations with PdBI and ALMA, their full characterization had been hindered by the large beams of single-dish observations that made it challenging to identify their optical and infrared counterparts. The ALESS survey has followed-up a sample of >100 SMGs in the Chandra Deep Field South with ALMA, allowing us to compile the multi-wavelength spectral energy distributions (SEDs) of a statistically reliable survey of SMGs.

I will present a recent calibration of the MAGPHYS spectral energy distribution (SED) modelling code that is optimized to interpret these UV-to-radio SEDs of dusty high-redshift sources. We derive statistically and physically robust estimates of the photometric redshifts and physical parameters (stellar masses, ages, star formation rates, dust masses) for the ALESS SMGs. Our modelling shows that our energy balance technique still successfully reproduces the observed SEDs in this highly obscured regime, and allow us to investigate the distribution of SMGs in the so-called ?star-forming main sequence? of galaxies. Finally, I will briefly describe preliminary results from newly-acquired ALMA observations of these sources.