3D-Herschel: Constraining Dust Emission with Panchromatic Modeling of 3D-HST Galaxies

We present 3D-Herschel, a new publicly released 0.3-350$\mu$m photometric catalog that combines deblended Herschel far-infrared (FIR) imaging with the CANDELS/3D-HST legacy fields to probe the dust-obscured universe. Using the 17-parameter Bayesian fitting code Prospector-$\beta$, we model 41,387 galaxies spanning 0.5 $< z <$ 2.5 to measure stellar and dust properties. Comparing fits with and without FIR constraints, we find that for the 3.2$\%$ of galaxies with $>3 \sigma$ detections in $\geq2$ Herschel bands, UV-MIR-only models (0.3-24$\mu$m) recover robust stellar ages, SFRs, and stellar masses (50-70$\%$ within the median 1$\sigma$ error). Consequently, the Prospector-$\beta$ star-forming sequence is unchanged by the inclusion of FIR data (average deviation 0.1$\pm$0.07 dex between UV-MIR and UV-FIR fits at fixed stellar mass), confirming that the offset relative to UV+IR-based estimates reported by Leja et al. 2022 is robust to the lack of direct FIR constraints. However, the use of rigid log-average IR templates with fixed dust emission parameters ($\gamma$, $U_{\mathrm{min}}$, $q_{\mathrm{PAH}}$) in UV-MIR modeling yields cold dust temperatures ($\sim$7K colder than Herschel-informed fits at all redshifts) and an unevolving MIR-to-IR luminosity ratio, with $\sim$0.2 dex lower IR-to-7.7$\mu$m luminosity ratios at the low-mass end of Herschel-detected galaxies (log($M_{\star}$) $\sim$ 9.6 $M_{\odot}$). These results demonstrate that MIR-to-IR conversions depend on stellar mass, cautioning against $L_{\mathrm{IR}}$-independent templates without FIR data. For galaxies with $<10^{11} \ M_{\odot}$ at $z>1.5$, Herschel can at best provide upper limits due to source confusion; next-generation FIR telescopes will be essential for distant galaxies.