On the physical properties of a flux-limited sample of ACT-Selected DSFGs: the case for multiplicity and the need for AtLAST

We model the far-infrared spectral energy distributions (SEDs) of 71 dusty star-forming galaxies (DSFGs) selected at millimeter wavelengths by the Atacama Cosmology Telescope (ACT) with a lower flux density limit of 8 mJy at 220 GHz (1.4 mm). All candidates were cross-identified with detections in the Herschel Stripe 82 Survey (HerS) and HerMES Large Mode Survey (HELMS) at 500, 350, and 250 ?m. We employ the probabilistic cataloging (PCAT) algorithm to decompose Herschel fluxes into multiple components, and further explore the physical nature of the DSFGs. We obtained targeted observations of nineteen of our sources using the Submillimeter Array (SMA) telescope to acquire high resolution imaging and flux extraction to compare to the ACT 220 GHz flux as well as assess the validity of the case for multiple components. Thirteen of these nineteen sources are evidenced to have missing flux in the single dish observations or have multiple components/extended structure. In this talk, I will present these findings and discuss the physical properties of the galaxies if they are treated as single sources with flux densities indicated by the single dish observations. I will then highlight the need for AtLAST for the more efficient mapping of DSFG environments out to high redshift.