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Arxiv: A Search for z=5 Hα and Hβ+[O III] Dual-Line Emitting Galaxies in the JWST CEERS Field: Implications for the AGN Abundance Published: 9/28/2024 4:40:12 AM Updated: 9/28/2024 4:40:12 AM

Paper abstract: The James Webb Space Telescope (JWST) has enabled us to uncover faintgalaxies and active galactic nuclei (AGNs) in the early universe. Takingadvantage of the unique filter combination used in the Cosmic Evolution EarlyRelease Science Survey (CEERS) program, we perform an extensive photometricsearch of galaxies emitting strong H\beta+[O III] and H\alpha lines. Theredshift range of the galaxies is limited to 5.03<= z<= 5.26 by requiringphotometric excesses in NIRCam's F277W and F410M images. A total of 261H\beta+[O III] and H\alpha dual-line emitters are found over the absoluteUV magnitude -22<~ M_{\mathrm{UV}}<~ -17, with a mean rest-frameequivalent width of 1010 A for H\beta+[O III] and 1040 A for H\alpha. Thispopulation accounts for ~ 40\% of the Lyman break galaxies at thisredshift range. Intriguingly, there are 58 objects (22% of the whole sample)that exhibit compact morphology at the rest-UV or optical wavelength. With anassumption that these compact dual-line emitters are dominated by AGN, theirAGN bolometric luminosities are in the range of 2\times 10^{43} <~L_{\rm bol}/({\rm erg~s}^{-1})<~ 3\times 10^{44}. Their number densityis two orders of magnitude higher than the extrapolation from the UV-selectedluminous quasars, which is in good agreement with previous JWST studies ofbroad-line AGNs, requiring a ~ 10\% of the AGN duty cycle. Moreover, ourdual-line emitter sample reaches the faint end of the H\alpha and [O III]luminosity functions down to <~ 10^{42}~{\rm erg~s}^{-1}. Spectroscopicfollow-up observations are planned in an approved JWST Cycle 3 program, inwhich we aim to confirm their nature, characterize their black hole activity,and construct their mass distribution at 10^6<~ M_{\rm BH}/M_\odot<~ 10^8.