Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Christina C. Williams, Stacey Alberts, Zhiyuan Ji, Kevin N. Hainline, Jianwei Lyu
| Summary:
Using deep JWST imaging from JADES, JEMS and SMILES, we characterize
optically-faint and extremely red galaxies at $z>3$ that were previously
missing from galaxy census estimates. The data indicate the existence of
abundant, dusty and post-starburst-like galaxies down to $10^8$M$_odot$, below
the sensitivity limit of Spitzer and ALMA. Modeling the NIRCam and HST
photometry of these red sources can result in extreme, high values for both
stellar mass and star formation rate (SFR); however, including 7 MIRI filters
out to 21$mu$m results in decreased mass (median 0.6 dex for
log$_{10}$M$^*$/M$_{odot}>$10), and SFR (median 10$times$ for SFR$>$100
M$_{odot}$/yr). At $z>6$, our sample includes a high fraction of little red
dots (LRDs; NIRCam-selected dust-reddened AGN candidates). We significantly
measure older stellar populations in the LRDs out to rest-frame 3$mu$m (the
stellar bump) and rule out a dominant contribution from hot dust emission, a
signature of AGN contamination to stellar population measurements. This allows
us to measure their contribution to the cosmic census at $z>3$, below the
typical detection limits of ALMA ($L_{rm IR}<10^{12}L_odot$). We find that
these sources, which are overwhelmingly missed by HST and ALMA, could
effectively double the obscured fraction of the star formation rate density at
$4<z<6$ compared to some estimates, showing that prior to JWST, the obscured
contribution from fainter sources could be underestimated. Finally, we identify
five sources with evidence for Balmer breaks and high stellar masses at
$5.5<z<7.7$. While spectroscopy is required to determine their nature, we
discuss possible measurement systematics to explore with future data.
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