CEERS: Possibly forging the first dust grains in the universe

A population of galaxies with spectroscopically derived extremely low dust attenuation (GELDA) at 4.0 < z ≲ 11.4

¹ Aix Marseille Université, CNRS, CNES, LAM, Marseille, France
² National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
³ NSF's National Optical-Infrared Astronomy Research Laboratory, 950 N. Cherry Ave., Tucson, AZ 85719, USA
⁴ Department of Astronomy, The University of Texas at Austin, Austin, TX, USA
⁵ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, 06000 Nice, France
⁶ Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
⁷ Institute for Computational and Data Sciences, The Pennsylvania State University, University Park, PA 16802, USA
⁸ Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
⁹ Space Telescope Science Institute, Baltimore, MD, USA
¹⁰ Instituto de Investigación Multidisciplinar en Ciencia y Tecnologí a, Universidad de La Serena, Raul Bitràn 1305, La Serena 2204000, Chile
¹¹ Department of Astronomy, The University of Texas at Austin, Austin, TX, USA
¹² Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
¹³ INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
¹⁴ Physics & Astronomy Department, University of Louisville, 40292 KY, Louisville, USA
¹⁵ Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623, USA
¹⁶ Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
¹⁷ Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, USA
¹⁸ Department of Physics and Astronomy, Colby College, Waterville, ME 04901, USA
¹⁹ Department of Physics and Astronomy, University of California, 900 University Ave, Riverside, CA 92521, USA
²⁰ Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843-4242, USA
²¹ George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX 77843-4242, USA
²² Centro de Astrobiologia (CAB), CSIC-INTA, Ctra. de Ajalvir km 4, Torrejon de Ardoz, E-28850 Madrid, Spain
²³ ESA/AURA Space Telescope Science Institute, Baltimore, MD 21218, USA
²⁴ Astrophysics Science Division, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
²⁵ Center for Research and Exploration in Space Science and Technology II, Department of Physics, Catholic University of America, 620 Michigan Ave N.E., Washington DC 20064, USA
²⁶ Department of Physics and Astronomy, Università degli Studi di Padova, Vicolo dell’Osservatorio 3, I-35122 Padova, Italy
²⁷ Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USA
²⁸ Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH, UK
²⁹ Institute of Space Sciences and Astronomy, University of Malta, Msida MSD 2080, Malta
³⁰ Nanjing Institute of Astronomical Optics and Technology, Nanjing 210042, China
³¹ University of Massachusetts Amherst, 710 North Pleasant Street, Amherst, MA 01003-9305, USA

^⋆ Corresponding author: denis.burgarella@lam.fr

Received: 22 February 2025
Accepted: 7 May 2025

Abstract

Aims. This work aims to investigate the coevolution of metals and dust for 173 galaxies at 4.0 < z ≤ 11.4 spectroscopically observed by the NIRSpec instrument onboard the James Webb Space Telescope (JWST) in the Cosmic Evolution Early Release Science Survey (CEERS) project. More specifically, we want to study and analyse the properties of a sample of galaxies that show an extremely low dust attenuation and try to understand the possible physical processes at play in these galaxies.

Methods. We developed a new version of the CIGALE code that accepts spectroscopic and photometric data. From a statistical comparison of the observations with the modelled spectra, we derived a set of physical parameters that allowed us to constrain the above physical processes.

Results. Our analysis reveals a population of 49 extremely low-dust-attenuation galaxies (GELDAs) consistent with A_FUV = 0.0 within 2σ_{A_FUV} and M_star<10⁹ M_⊙. After stacking the spectra of the 49 GELDAs to increase the signal-to-noise ratio, we measured a very blue UV slope of β_FUV=−2.451±0.066 and a Balmer decrement of Hα/Hβ = 2.932±0.660 without underlying absorption and consistent with no dust attenuation; Case B assumes an underlying absorption of 2.5%. Furthermore, the proportion of GELDAs is much higher at z > 8.8 (83.3% of the total sample) than at z < 8.8 (26.3% of the total sample). This suggests that GELDAs became dominant in the early Universe. Assuming a prior far-infrared dust spectrum from the ALPINE sample, we performed an analysis of the properties of this galaxy population. The trends observed in the M_dust versus M_star diagram feature an upper and a lower sequence linked by objects that can be transitional. A comparison with models suggests that we might observe a critical transition at M_star≈10^8.5 M_⊙, corresponding to a critical metallicity of Z_crit = 12+log₁₀(O/H) ≈ 7.60 (i.e. Z/Z_⊙≈0.1). At this point, galaxies transition from being dominated by stellar-dust production (mainly from supernovae) to grain growth through gas–dust accretion in the ISM. The observational critical metallicity Z_crit derived in this paper is in good agreement with predictions from theoretical models for the onset of efficient grain growth. Furthermore, the mean gas-mass fraction of our entire sample at 4.0 < z < 11.4 is very high: f_gas≳0.9. All of our galaxies, including GELDAs at all redshifts, contain a large amount of gas that was not expelled from the galaxies. Finally, the small size of the galaxies combined with the mass of gas lead to very high surface-gas densities – which put our sample below high-redshift sub-millimeter galaxies – at relatively low star formation efficiency. The population of high-redshift GELDAs would provide us with a natural and inherent explanation for the origin of the apparent tension between observations and theoretical models in the number density of bright galaxies at z ≳ 9.