Revealing galaxy candidates out to z ∼ 16 with JWST observations of the lensing cluster SMACS0723

Abstract

One of the main goals of the JWST is to study the first galaxies in the Universe. We present a systematic photometric analysis of very distant galaxies in the first JWST deep field towards the massive lensing cluster SMACS0723. As a result, we report the discovery of two galaxy candidates at z ∼ 16, only 250 million years after the big bang. We also identify two candidates at z ∼ 12 and 6 candidates at z ∼ 9 − 11. Our search extended out to z ≲ 21 by combining colour information across seven NIRCam and NIRISS filters. By modelling the Spectral Energy Distributions (SEDs) with EAZY and BEAGLE, we test the robustness of the photometric redshift estimates. While their intrinsic (un-lensed) luminosity is typical of the characteristic luminosity L* at z > 10, our high-redshift galaxies typically show small sizes and their morphologies are consistent with disks in some cases. The highest-redshift candidates have extremely blue UV-continuum slopes −3 < β < −2.4, young ages ∼10 − 100 Myr, and stellar masses around log (M⋆/M⊙) = 8.8 inferred from their SED modeling, which indicate a rapid build-up of their stellar mass. Our search clearly demonstrates the capabilities of JWST to uncover robust photometric candidates up to very high redshifts, and peer into the formation epoch of the first galaxies.

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

“…3.6.5. Atek et al (2023) Using the ERO data set in the SMACS J0723 field, Atek et al (2023) selected 10 galaxy candidates at 10 < z < 16. We refer to manuscript version 2, which was submitted to arXiv on October 31.…”

“…The mass models of the ERO target cluster, SMACS J0723, are improved with the NIRCam imaging and NIRSpec spectroscopic data (Caminha et al 2022;Mahler et al 2022;Pascale et al 2022). High-redshift galaxies are searched in the ERO SMACS J0723 and ERS CEERS and GLASS fields, and are identified at z ∼ 9-20 (Adams et al 2023;Atek et al 2023;Castellano et al 2022;Donnan et al 2023;Finkelstein et al 2022b;Leethochawalit et al 2022;Morishita & Stiavelli 2022;Naidu et al 2022b;Yan et al 2023). The morphological properties are investigated with the NIRCam images of the ERO SMACS J0723 and the CEERS observations via the comparisons of HST images for galaxies at z ∼ 3-6 (Ferreira et al 2022) and the rest-frame optical and near-infrared bands for galaxies at z ∼ 1-2 (Suess et al 2022), respectively.…”

High-redshift JWST Observations and Primordial Non-Gaussianity

“…The initial James Webb Space Telescope (JWST) imaging via early release programs, such as Cosmic Evolution Early Release Science (CEERS), early release observations, and early release science (ERS), has recently reported a population of surprisingly massive galaxy candidates at redshifts of z  8 with stellar masses of the order of 10 9 M e (Atek et al 2023;Finkelstein et al 2022;Harikane et al 2022;Naidu et al 2022;Yan et al 2022). Even though a spectroscopic follow-up will be necessary to confirm these observations based on photometry only, the early formation of massive galaxies reported by the JWST is hardly reconcilable with the standard ΛCDM expectations, which would require an implausible high star formation efficiency (SFE), even larger than the cosmic baryon mass budget in collapsed structures.…”

First Light And Reionisation Epoch Simulations (FLARES) XI: [OIII] emitting galaxies at $5

“…This has allowed us to identify samples of 𝑧 > 10 galaxies for the first time (e.g. Adams et al 2023;Atek et al 2023;Castellano et al 2022;Donnan et al 2022;Finkelstein et al 2022;Naidu et al 2022), probe the restframe optical spectral energy distributions at 𝑧 > 6 (e.g. Adams et al 2023), and study optical morphologies to high-redshift (e.g.…”