Impact of stochastic star formation histories and dust information on selecting quiescent galaxies with JWST photometry

¹ National Centre for Nuclear Research, Pasteura 7, 093 Warsaw, Poland
² SISSA, Via Bonomea 265, 34136 Trieste, Italy
³ Department of Physics & Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver BC V6T 1Z1, Canada
⁴ Department of Astronomy and Physics, Saint Mary’s University, 923 Robie Street, Halifax NS B3H 3C3, Canada
⁵ Canada Research Chair in Astronomy and Astrophysics (Tier II), Canada
⁶ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁷ INAF, OAPD, Vicolo dell’Osservatorio, 5, 35122 Padova, Italy
⁸ Dipartimento di Fisica e Astronomia, Universitá di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
⁹ Department of Astronomy, The University of Washington, Seattle, WA, USA
¹⁰ Instituto de Astrofísica de Canarias, Vía Láctea S/N, E-38205 La Laguna, Spain
¹¹ Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Spain
¹² Kavli Institute for Cosmology Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹³ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹⁴ Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut Mönchhofstr, 12-14 69120 Heidelberg, Germany
¹⁵ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
¹⁶ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudzidzka 5, 87-100 Toruń, Poland
¹⁷ Astronomical Observatory of the Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 5 September 2025
Accepted: 25 February 2026

Abstract

Context. The James Webb Space Telescope (JWST) enables the identification of quiescent galaxies out to early epochs, offering a transformative view of their evolution. However, the photometric selection of quiescent galaxy candidates (QGCs) and the derivation of their key physical quantities, such as stellar masses (M_★) and dust attenuation, remain highly sensitive to the assumed star formation histories (SFHs), where dust–age degeneracies and modelling choices continue to stand as a major source of uncertainty.

Aims. We aim to quantify how the inclusion of JWST/MIRI data and different SFH models impacts the selection and characterisation of QGCs. We test the robustness of the physical properties inferred from the spectral energy distribution (SED) fitting, such as M_★, age, star formation rate (SFR), and dust attenuation (A_V). We study how these parameters impact the quiescence criteria of the galaxies across cosmic time.

Methods. We performed SED fittings for ∼13 000 galaxies at z ≤ 6 from the CEERS/MIRI fields with a ≤20 optical to mid-infrared broadband coverage. We implemented three SFH prescriptions: a flexible delayed model, a non-parametric model, and an extended regulator model. For each SFH, we compared the results obtained with and without MIRI photometry and dust emission models. We evaluated the impact of these configurations on both the number of QGCs, selected on the basis of their rest-frame UVJ colours, specific SFR, and main-sequence offset, as well as on their key physical properties, such as M_★, A_V, and stellar ages.

Results. The number of selected QGCs varied significantly, with the SFH ranging from 70 to 100 out of a mass-complete sample of ∼5000 galaxies, depending on the model. This number increased to 103–180 when MIRI data were included, driven by improved constraints on both dust attenuation and M_★. We found a strong correlation between A_V and M_★ of QGCs at z ≤ 2.5, with massive galaxies (M_★ ∼ 10¹¹ M_⊙) shown to be ∼ 1.5 − 4 times more attenuated than low-mass galaxies (M_★ ∼ 10⁹ M_⊙). Regardless of the SFH, ∼13% of QGCs exhibit significant attenuation (A_V > 0.5) in support of recent JWST results on dust-rich quiescent galaxy candidates.