SCUBADive II: Searching for $z>4$ Dust-Obscured Galaxies via F150W-Dropouts in COSMOS-Web
Sinclaire M. Manning, Jed McKinney, Katherine E. Whitaker, Arianna S. Long, Olivia R. Cooper, Caitlin M. Casey, Rafael C. Arango-Toro, Jaclyn B. Champagne, Nicole E. Drakos, Andreas L. Faisst, Maximilien Franco, Ghassem Gozaliasl, Santosh Harish, Hossein Hatamnia, Christopher C. Hayward, Michaela Hirschmann, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Daizhong Liu, Georgios E. Magdis, Henry Joy McCracken, Jason Rhodes, Brant E. Robertson, Margherita Talia, Francesco Valentino, John R. Weaver, Jorge A. Zavala
TL;DR
The paper tackles the uncertain prevalence of dust-obscured galaxies at $z>4$ by assembling SCUBADive, a JWST+ALMA counterpart catalog for COSMOS-Web DSFGs, and uses it to identify distant, dark galaxies via the F150W-dropout technique. It identifies 60 F150W-dropouts, including 16 AzTECC71-like systems, with a mean star formation rate of $450^{+920}_{-320}$ $M_\odot$ yr$^{-1}$ and a mean stellar mass of $\log_{10}(M_*/M_\odot)=11.2^{+0.5}_{-0.6}$, noting that these sources may not be extreme for their epoch. Heavily obscured galaxies constitute $\gtrsim20\%$ of galaxies across mass bins and potentially up to $60\%$ at the highest masses ($\log_{10}(M_*/M_\odot)>11.5$) of the $z>4$ stellar mass function, underscoring their significance for mass assembly in the early universe. The work demonstrates the efficacy of integrating JWST data with submillimeter observations to reveal a substantial obscured population missed by optical surveys, with important implications for galaxy evolution models and the high-$z$ stellar mass function.
Abstract
The relative fraction of obscured galaxies at $z>4$ compared to lower redshifts remains highly uncertain as accurate bookkeeping of the dust-obscured component proves difficult. We address this shortcoming with SCUBADive, a compilation of the JWST counterparts of (sub-)millimeter galaxies in COSMOS-Web, in order to further analyze the distribution and properties of massive dust-obscured galaxies at early times. In this paper, we present a subset of SCUBADive, focusing on 60 ``dark'' galaxies that dropout at 1.5\micron. Motivated by JWST observations of AzTECC71, a far-infrared bright F150W-dropout with $z_{\rm phot}=5.7^{+0.8}_{-0.7}$, we complete a systematic search of F150W-dropouts with SCUBA-2 and ALMA detections to find more candidate high redshift dusty galaxies. Within our subsample, 16 are most similar to AzTECC71 due to fainter F444W magnitudes ($>24$\,mag) and lack of counterparts in COSMOS2020. Despite high star formation rates ($\langle$SFR$\rangle=450^{+920}_{-320}$\,\mdot\,yr$^{-1}$) and large stellar masses ($\langle$log$_{10}$(\mstar)$\rangle=11.2^{+0.5}_{-0.6}$\,\mdot) on average, these galaxies may not be particularly extreme for their presumed epochs according to offsets from the main sequence. We find that heavily obscured galaxies, which would be missed by pre-JWST optical imaging campaigns, comprise $\gtrsim20$\% of galaxies across mass bins and potentially contribute up to 60\% at the very high mass end (log$_{10}$(\mstar/\mdot)$>11.5$) of the $z>4$ stellar mass function.