2026ApJ...996..104H

We report the modeling of the millimeter and far-infrared (FIR) spectral energy distributions (SEDs) of 71 dusty star-forming galaxies (DSFGs) selected by the Atacama Cosmology Telescope (ACT) with a 5σ flux density limit of 8 mJy at 220 GHz (1.4 mm). All sources were cross-identified with Herschel surveys at 500, 350, and 250 μm, and 19 of our sources were observed with the Submillimeter Array (SMA). A probabilistic cataloging (PCAT) algorithm favors multiple unresolved flux components in the Herschel data for the majority of ACT-selected DSFGs. We compare the derived physical properties of the DSFGs obtained from modeling the flux densities with those from similar studies of DSFG populations. We find the median, 16th, and 84th percentiles for the following SED model parameters: redshift ${z}_{{\rm{phot}}}=3.{3}_{-0.6}^{+0.7}$, apparent size $\sqrt{\mu }d=5.{2}_{-2.4}^{+0.9}\,{\rm{kpc}}$, apparent dust mass ${\mathrm{log}}_{10}\,(\mu {M}_{d}/{M}_{\odot })=9.1{4}_{-0.04}^{+0.12}$, and cutoff temperature ${T}_{c}=35.{6}_{-1.6}^{+4.8}\,{\rm{K}}$ for a power-law distribution, and the corresponding apparent FIR luminosity ${\mathrm{log}}_{10}\,(\mu {L}_{{\rm{IR}}}/{L}_{\odot })=13.{6}_{-0.3}^{+0.2}$, where μ is the lensing magnification. While many of the properties broadly agree with those of samples of primarily lensed DSFGs, we exercise caution in interpreting them. ACT's lower flux limit, the PCAT decomposition, and the SMA observations all suggest that some fraction of these DSFGs are likely to be unlensed and possibly multiples. The SMA data indicate that at least 14 out of 19 sources are such, either via “missing” flux in comparison to the model or detection of additional sources in the fields. Additional high-resolution follow-up and redshift determination are needed to better understand this flux-limited sample of DSFGs.