A Comprehensive Study on Galaxies at z~9-16 Found in the Early JWST Data: UV Luminosity Functions and Cosmic Star-Formation History at the Pre-Reionization Epoch

Abstract

We conduct a comprehensive study on dropout galaxy candidates at z ∼ 9 − 17 using the first 90 arcmin 2 JWST/NIRCam images taken by the early release observations (ERO) and early release science (ERS) programs. With the JWST simulation images, we find that a number of foreground interlopers are selected with a weak photo-z determination (∆χ 2 > 4). We thus carefully apply a secure photo-z selection criterion (∆χ 2 > 9) and conventional color criteria with confirmations of the ERO NIRSpec spectroscopic redshifts, and obtain a total of 25 dropout galaxies at z ∼ 9−17, including two candidates at z phot = 16.45 +0.09 −0.32 and 16.66 +1.86 −0.34 . 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 − 17, and confirm that our UV luminosity functions at z ∼ 9 and 12 agree with those determined by previous HST and JWST studies. The cosmic star-formation rate density decreases from z ∼ 9 to 12, and perhaps to 17, but the densities at z ∼ 12 − 17 are higher than the constant star formation efficiency model. Interestingly, there are six bright galaxy candidates at z ∼ 11 − 17 with M UV < −19.5 whose stellar masses are very high, 10 8−9 M . Because a majority (∼ 70%) of these galaxies shows no signatures of AGNs in their morphologies, the high cosmic star-formation rate densities and the existence of these stellar massive galaxies are explained by no suppression of star-formation by the UV background radiation at the pre-reionization epoch or an efficient UV radiation production by Population III-like star formation.

Schrodinger's Galaxy Candidate: Puzzlingly Luminous at $z\approx17$, or Dusty/Quenched at $z\approx5$?

“…CEERS-1749 was also recently reported by Donnan et al (2022, see also Harikane et al 2022a), in their search for z > 10 candidates across the JWST ERS data, as lying at z = 16.6. They infer a slightly lower mass of log(M /M ) = 9.0 ± 0.4.…”

“…This paper follows an earlier analysis of Naidu et al (2022a), who identified the most luminous galaxy candidates in the existing ERS imaging data, based on optical non-detection criteria and photometric redshift measurements using the EAZY code (Brammer et al 2008). As first noted in that paper, the CEERS field revealed a seemingly reliable, but extremely luminous galaxy candidate with photometric redshift at z = 16.6 ± 0.1 (see also Donnan et al 2022;Harikane et al 2022a). Given its extraordinary luminosity, if confirmed to lie at z ∼ 17, this source deserved special attention and analysis.…”

“…Here, we present a detailed analysis of an extremely luminous z ∼ 17 galaxy candidate identified in the Early Release Science (ERS) program CEERS (Finkelstein et al 2022). The source was first mentioned in Naidu et al (2022a) and presented as a likely z = 16.6 candidate in Donnan et al (2022) as well as Harikane et al (2022a). Here, we present a detailed analysis of this source, including arguments for a possible lower redshift solution of this galaxy at z ∼ 5 (see also Zavala et al 2022).…”

“…At the highest redshifts, JWST has finally pushed our observational frontier beyond z ∼ 11, into the last unknown epoch of our cosmic timeline. Several teams have reported a surprisingly large number of particularly luminous sources very early in the Universe's history (e.g., Naidu et al 2022a;Castellano et al 2022;Donnan et al 2022;Atek et al 2022;Yan et al 2022;Finkelstein et al 2022;Harikane et al 2022a).…”

JWST unveils heavily obscured (active and passive) sources up to z~13

“…• Extinguished high-𝑧 star-forming sources (8 < 𝑧 < 13): the daily recording of the farthest objects with JWST is currently providing candidates up to 𝑧 ∼ 17 (e.g. Harikane et al 2022). These sources are consistent with primordial young star forming galaxies, with a negligible dust content.…”