A Comprehensive Study of Galaxies at z ∼ 9–16 Found in the Early JWST Data: Ultraviolet Luminosity Functions and Cosmic Star Formation History at the Pre-reionization Epoch

By Y. Harikane, M. Ouchi, M. Oguri, Yoshiaki Ono, K. Nakajima, Y. Isobe, Hiroya Umeda, Kentarou Mawatari, Yechi Zhang. Astrophysical Journal Supplement Series, 2022

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We conduct a comprehensive study on dropout galaxy candidates at z ∼ 9–16 using the first 90 arcmin2 James Webb Space Telescope (JWST) Near Infrared Camera images taken by the early release observations (ERO) and early release science programs. With the JWST simulation images, we find that a number of foreground interlopers are selected with a weak photo-z determination (Δχ 2 > 4). We thus carefully apply a secure photo-z selection criterion (Δχ 2 > 9) and conventional color criteria with confirmations of the ERO Near Infrared Spectrograph spectroscopic redshifts, and obtain a total of 23 dropout galaxies at z ∼ 9–16, including two candidates at zphot=16.25−0.46+0.24 and 16.41−0.55+0.66 . We perform thorough comparisons of dropout galaxies found in our work with recent JWST studies, and conclude that our galaxy sample is reliable enough for statistical analyses. We derive the UV luminosity functions at z ∼ 9–16, and confirm that our UV luminosity functions at z ∼ 9 and 12 agree with those determined by other Hubble Space Telescope and JWST studies. The cosmic star formation rate (SFR) density decreases from z ∼ 9 to 12, and perhaps to 16, but the densities at z ∼ 12–16 are higher than the constant star formation efficiency model. Interestingly, there are six bright galaxy candidates at z ∼ 10–16 with M UV < −19.5 mag and M * ∼ 108−9 M ⊙. Because a majority (∼80%) of these galaxies show no signatures of active galactic nuclei in their morphologies, the high cosmic SFR densities and the existence of these UV-luminous galaxies are explained by the lack of suppression of star formation by the UV background radiation at the pre-reionization epoch and/or an efficient UV radiation production by a top-heavy initial mass function with Population III–like star formation.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/45f8a15d72637aa34b55022162585e2829cbd35f

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Citations in the corpus

The Complete CEERS Early Universe Galaxy Sample: A Surprisingly Slow Evolution of the Space Density of Bright Galaxies at z ∼ 8.5–14.5 (2023, methodology): “While some early results changed owing to the uncertain characterization of the NIRCam photometric zero-point ( Boyer et al. 2022 ) , within a few months more robust samples of galaxies were in place ( e.g., Harikane et al. 2023a; Finkelstein et al. 2023; McLeod et al. 2024 ) .”
CEERS Key Paper. I. An Early Look into the First 500 Myr of Galaxy Formation with JWST (2022, methodology): “…only the detection of objects at the expected redshifts of z∼ 10–11 (e.g., Adams et al. 2022; Castellano et al. 2022; Labbe et al. 2022; Naidu et al. 2022b; Whitler et al. 2023) but some candidates at z∼ 12–17 (e.g., Donnan et al. 2023, hereafter D23;Finkelstein et al. 2022b; Harikane et al. 2023).”
A JWST/NIRSpec First Census of Broad-line AGNs at z = 4–7: Detection of 10 Faint AGNs with M BH ∼ 106–108 M ⊙ and Their Host Galaxy Properties (2023, methodology): “We choose a flexible star formation history as adopted in Harikane et al. (2023) with a continuity prior.”
JWST Census for the Mass–Metallicity Star Formation Relations at z = 4–10 with Self-consistent Flux Calibration and Proper Metallicity Calibrators (2023, methodology): “Asacomplementary approach to our method using the [ N II ] BPT diagram, a companion study by Harikane et al. ( 2023b ) conducts a search for faint AGNs in our full JWST spectroscopic sample by examining the broad component ( FWHM > 1000 km s − 1 ) around the H α emission line.”