RSAA Colloquia / Seminars / Feast-of-Facts: Thursday, 12 November 2015, 11:00-12:00; Duffield Lecture Theatre

Elisabete da Cunha

"Understanding the most dusty galaxies in the Universe with ALMA"

Sub-millimeter galaxies (SMGs) are the most dusty galaxies in the high-redshift Universe, with large infrared luminosities powered by intense star formation activity. Although these galaxies are relatively rare, they are a crucial population to understand the broad picture of galaxy evolution. SMGs contribute up to half of the star formation rate density at z>1, and they are possibly the progenitors of the most massive galaxies found in the local Universe. Their large amounts of dust make them ideal objects to study how dust forms in the high-redshift interstellar medium (ISM), and to study the interplay between star formation activity, gas and dust. Up until recent interferometric observations with PdBI and ALMA, the full characterisation of SMGs 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 122 SMGs in the Chandra Deep Field South with ALMA, allowing us to compile the multi-wavelength spectral energy distributions (SEDs) of the most unbiased and statistically reliable survey of SMGs to date. I will present a new calibration of the MAGPHYS SED modelling code that is optimised to interpret these ultraviolet-to-radio high-redshift observations simultaneously. With this code, we derive statistically and physically robust estimates of the photometric redshifts and physical parameters (e.g. stellar masses, 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. To put the ALESS SMGs into context, we compare their stellar masses and star formation rates with those of mass-selected galaxies at the same redshifts, to understand where they are located in comparison to the observed ’star-forming main sequence’ of galaxies. Finally, I will discuss new avenues in understanding this population of galaxies with future ALMA programmes.