Discovery and properties of ultra-high redshift galaxies (9 < z < 12) in the JWST ERO SMACS 0723 Field

Abstract

We present a reduction and analysis of the James Webb Space Telescope (JWST) SMACS 0723 field using new post-launch calibrations to conduct a search for ultra-high-redshift galaxies (z > 9) present within the Epoch of Reionisation. We conduct this search by modelling photometric redshifts in several ways for all sources and by applying conservative magnitude cuts (mF200W < 28) to identify strong Lyman breaks greater than 1 magnitude. We find four z > 9 candidate galaxies which have not previously been identified, with one object at z = 11.5, and another which is possibly a close pair of galaxies. We measure redshifts for candidate galaxies from other studies and find the recovery rate to be only 23 per cent, with many being assigned lower redshift, dusty solutions in our work. Most of our z > 9 sample show evidence for Balmer-breaks, or extreme emission lines from Hβ and [OIII], demonstrating that the stellar populations could be advanced in age or very young depending on the cause of the F444W excess. We discuss the resolved structures of these early galaxies and find that the Sérsic indices reveal a mixture of light concentration levels, but that the sizes of all our systems are exceptionally small (<0.5 kpc). These systems have stellar masses M* ∼ 109.0 M⊙, with our z ∼ 11.5 candidate a dwarf galaxy with a stellar mass M* ∼ 107.8 – 108.2 M⊙. These candidate ultra high-redshift galaxies are excellent targets for future NIRSpec observations aimed to better understand their physical nature.

A Candidate for the Least-massive Black Hole in the First 1.1 Billion Years of the Universe

“…This process was needed to correct the preflight measurements applied in the original images. The difference of the pre-and postflight photometric reference files is significant, as is also discussed in Adams et al (2023). With the updated calibration, the F410M and F444W flux densities (in mega Jansky per steradian unit) decrease by 10%-20% in the two NIRCam detector modules.…”

“…The 6.5 m space observatory is expected to be a game changer in the field of extragalactic observations. Numerous papers have claimed the first detection of ultra high-redshift galaxies at z  10, waiting for spectroscopic confirmation (e.g., Adams et al 2023;Castellano et al 2022;Donnan et al 2023;Finkelstein et al 2022aFinkelstein et al , 2022bHarikane et al 2022b;Naidu et al 2022). Likewise, the superb sensitivity of JWST may also enable us to witness rapidly accreting seed BHs far beyond the current samples of high-redshift AGNs.…”

An upper limit on [O III] 88 μm and 1.2 mm continuum emission from a JWSTz ≈ 12–13 galaxy candidate with ALMA

“…One of the main science goals of the James Webb Space Telescope (JWST) is to detect the very first galaxies that formed after the Big Bang. Making use of the public release of the first JWST observations, a number of papers have reported new z > 10 galaxy candidates based on spectral energy distribution (SED) fitting of JWST near-infrared photometry (Adams et al 2022;Atek et al 2022;Bouwens et al 2022;Bradley et al 2022;Castellano et al 2022;Donnan et al 2023;Harikane et al 2022a;Hsiao et al 2022;Finkelstein et al 2022a;Labbe et al 2022;Naidu et al 2022a,b;Yan et al 2023;Finkelstein et al 2022b;Rodighiero et al 2023).…”

JWST's PEARLS: Bright 1.5–2.0 μm Dropouts in the Spitzer/IRAC Dark Field

“…These data were obtained in three different fields of similar coverage, namely, the JWST Early Release Observations (ERO; Pontoppidan et al 2022) in the SMACS J0723−73 cluster field (hereafter "SMACS0723"), the GLASS JWST Early Release Science Program (Treu et al 2022) in the flanking field of A2744 (hereafter "GLASS"), and the Cosmic Evolution Early Release Science Survey (hereafter "CEERS"; Finkelstein et al 2022) in the Extended Groth Strip. Within a month after these data were released, over a hundred candidate z > 11 galaxies have been reported (Adams et al 2023;Atek et al 2022;Castellano et al 2022;Donnan et al 2022;Finkelstein et al 2022;Harikane et al 2022;Naidu et al 2022a;Rodighiero et al 2023;Yan et al 2022) using either the dropout method that identifies the Lyman break or the photometric redshift (z ph ) method. The largest sample, from Yan et al (2022), contains 87 candidates up to z ≈ 20 in SMACS0723.…”