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CEERS Key Paper I: An Early Look into the First 500 Myr of Galaxy Formation with JWST

Steven L. Finkelstein, Micaela B. Bagley, Henry C. Ferguson, Stephen M. Wilkins, Jeyhan S. Kartaltepe, Casey Papovich, L. Y. Aaron Yung, Pablo Arrabal Haro, Peter Behroozi, Mark Dickinson, Dale D. Kocevski, Anton M. Koekemoer, Rebecca L. Larson, Aurelien Le Bail, Alexa M. Morales, Pablo G. Perez-Gonzalez, Denis Burgarella, Romeel Dave, Michaela Hirschmann, Rachel S. Somerville, Stijn Wuyts, Volker Bromm, Caitlin M. Casey, Adriano Fontana, Seiji Fujimoto, Jonathan P. Gardner, Mauro Giavalisco, Andrea Grazian, Norman A. Grogin, Nimish P. Hathi, Taylor A. Hutchison, Saurabh W. Jha, Shardha Jogee, Lisa J. Kewley, Allison Kirkpatrick, Arianna S. Long, Jennifer M. Lotz, Laura Pentericci, Justin D. R. Pierel, Nor Pirzkal, Swara Ravindranath, Russell E. Ryan, Jonathan R. Trump, Guang Yang, Rachana Bhatawdekar, Laura Bisigello, Veronique Buat, Antonello Calabro, Marco Castellano, Nikko J. Cleri, M. C. Cooper, Darren Croton, Emanuele Daddi, Avishai Dekel, David Elbaz, Maximilien Franco, Eric Gawiser, Benne W. Holwerda, Marc Huertas-Company, Anne E. Jaskot, Gene C. K. Leung, Ray A. Lucas, Bahram Mobasher, Viraj Pandya, Sandro Tacchella, Benjamin J. Weiner, Jorge A. Zavala

TL;DR

The paper leverages the first-epoch JWST CEERS NIRCam data to push galaxy studies into the first 500 million years by identifying robust z>9 candidates. A detailed, simulation-backed photometric pipeline combines HST and JWST imaging, with careful background subtraction and PSF matching to produce accurate colors and total fluxes, enabling reliable photometric redshifts. The authors identify 26 galaxy candidates at z~9–16, find compact morphologies with a median half-light radius of ~0.5 kpc, and present an early estimate of the z~11 rest-frame UV luminosity function. Their results hint at a high-number density of ultra-high-redshift galaxies relative to most theoretical predictions, implying possible top-heavy IMFs or alternative physics (e.g., minimal dust attenuation) in the early universe, underscoring JWST’s potential to revolutionize our view of early galaxy formation.

Abstract

We present an investigation into the first 500 Myr of galaxy evolution from the Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one of 13 JWST ERS programs, targets galaxy formation from z~0.5 to z>10 using several imaging and spectroscopic modes. We make use of the first epoch of CEERS NIRCam imaging, spanning 35.5 sq. arcmin, to search for candidate galaxies at z>9. Following a detailed data reduction process implementing several custom steps to produce high-quality reduced images, we perform multi-band photometry across seven NIRCam broad and medium-band (and six Hubble broadband) filters focusing on robust colors and accurate total fluxes. We measure photometric redshifts and devise a robust set of selection criteria to identify a sample of 26 galaxy candidates at z~9-16. These objects are compact with a median half-light radius of ~0.5 kpc. We present an early estimate of the z~11 rest-frame ultraviolet (UV) luminosity function, finding that the number density of galaxies at M_UV ~ -20 appears to evolve very little from z~9 to z~11. We also find that the abundance (surface density [arcmin^-2]) of our candidates exceeds nearly all theoretical predictions. We explore potential implications, including that at z>10 star formation may be dominated by top-heavy initial mass functions, which would result in an increased ratio of UV light per unit halo mass, though a complete lack of dust attenuation and/or changing star-formation physics may also play a role. While spectroscopic confirmation of these sources is urgently required, our results suggest that the deeper views to come with JWST should yield prolific samples of ultra-high-redshift galaxies with which to further explore these conclusions.

CEERS Key Paper I: An Early Look into the First 500 Myr of Galaxy Formation with JWST

TL;DR

The paper leverages the first-epoch JWST CEERS NIRCam data to push galaxy studies into the first 500 million years by identifying robust z>9 candidates. A detailed, simulation-backed photometric pipeline combines HST and JWST imaging, with careful background subtraction and PSF matching to produce accurate colors and total fluxes, enabling reliable photometric redshifts. The authors identify 26 galaxy candidates at z~9–16, find compact morphologies with a median half-light radius of ~0.5 kpc, and present an early estimate of the z~11 rest-frame UV luminosity function. Their results hint at a high-number density of ultra-high-redshift galaxies relative to most theoretical predictions, implying possible top-heavy IMFs or alternative physics (e.g., minimal dust attenuation) in the early universe, underscoring JWST’s potential to revolutionize our view of early galaxy formation.

Abstract

We present an investigation into the first 500 Myr of galaxy evolution from the Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one of 13 JWST ERS programs, targets galaxy formation from z~0.5 to z>10 using several imaging and spectroscopic modes. We make use of the first epoch of CEERS NIRCam imaging, spanning 35.5 sq. arcmin, to search for candidate galaxies at z>9. Following a detailed data reduction process implementing several custom steps to produce high-quality reduced images, we perform multi-band photometry across seven NIRCam broad and medium-band (and six Hubble broadband) filters focusing on robust colors and accurate total fluxes. We measure photometric redshifts and devise a robust set of selection criteria to identify a sample of 26 galaxy candidates at z~9-16. These objects are compact with a median half-light radius of ~0.5 kpc. We present an early estimate of the z~11 rest-frame ultraviolet (UV) luminosity function, finding that the number density of galaxies at M_UV ~ -20 appears to evolve very little from z~9 to z~11. We also find that the abundance (surface density [arcmin^-2]) of our candidates exceeds nearly all theoretical predictions. We explore potential implications, including that at z>10 star formation may be dominated by top-heavy initial mass functions, which would result in an increased ratio of UV light per unit halo mass, though a complete lack of dust attenuation and/or changing star-formation physics may also play a role. While spectroscopic confirmation of these sources is urgently required, our results suggest that the deeper views to come with JWST should yield prolific samples of ultra-high-redshift galaxies with which to further explore these conclusions.
Paper Structure (7 sections, 1 figure)

This paper contains 7 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Data
  3. Data Reduction
  4. HST Imaging Data
  5. Photometry
  6. Background Subtraction
  7. Point-Spread Function Matching

Figures (1)

  • Figure 1: An example of the results of our background subtraction procedure. The left panel shows a zoom in on the science image of the ALONG module of our F444W mosaic in the CEERS1 pointing. The middle panel is the derived background, and the right panel is the background-subtracted science image. By progressively masking out objects in smaller tiers, this method is able to capture both small and large-scale fluctuations. Full details on this process are available in bagley22b.