Kavli Affiliate: Kohei Inayoshi
| First 5 Authors: Jingsong Guo, Masafusa Onoue, Kohei Inayoshi, Dale D. Kocevski, Steven L. Finkelstein
| Summary:
The James Webb Space Telescope (JWST) has enabled us to uncover faint
galaxies and active galactic nuclei (AGNs) in the early universe. Taking
advantage of the unique filter combination used in the Cosmic Evolution Early
Release Science Survey (CEERS) program, we perform an extensive photometric
search of galaxies emitting strong H$beta+$[O III] and H$alpha$ lines. The
redshift range of the galaxies is limited to $5.03leq zleq 5.26$ by requiring
photometric excesses in NIRCam’s F277W and F410M images. A total of 261
H$beta+$[O III] and H$alpha$ dual-line emitters are found over the absolute
UV magnitude $-22lesssim M_{mathrm{UV}}lesssim -17$, with a mean rest-frame
equivalent width of 1010 A for H$beta+$[O III] and 1040 A for H$alpha$. This
population accounts for $sim 40%$ of the Lyman break galaxies at this
redshift range. Intriguingly, there are 58 objects (22% of the whole sample)
that exhibit compact morphology at the rest-UV or optical wavelength. With an
assumption that these compact dual-line emitters are dominated by AGN, their
AGN bolometric luminosities are in the range of $2times 10^{43} lesssim
L_{rm bol}/({rm erg~s}^{-1})lesssim 3times 10^{44}$. Their number density
is two orders of magnitude higher than the extrapolation from the UV-selected
luminous quasars, which is in good agreement with previous JWST studies of
broad-line AGNs, requiring a $sim 10%$ of the AGN duty cycle. Moreover, our
dual-line emitter sample reaches the faint end of the H$alpha$ and [O III]
luminosity functions down to $lesssim 10^{42}~{rm erg~s}^{-1}$. Spectroscopic
follow-up observations are planned in an approved JWST Cycle 3 program, in
which we aim to confirm their nature, characterize their black hole activity,
and construct their mass distribution at $10^6lesssim M_{rm BH}/M_odot
lesssim 10^8$.
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