MIDIS

Near-infrared rest-frame morphology of massive galaxies at 3 < z < 5 in the Hubble eXtreme Deep Field

¹ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Ajalvir km 4, Torrejón de Ardoz, E-28850 Madrid, Spain
² Cosmic Dawn Center (DAWN), Copenhagen, Denmark
³ DTU-Space, Technical University of Denmark, Elektrovej 327, DK-2800 Kgs. Lyngby, Denmark
⁴ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁵ Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700AV Groningen, The Netherlands
⁶ Department of Astronomy, Stockholm University, Oscar Klein Centre, AlbaNova University Centre, 106 91 Stockholm, Sweden
⁷ Dept. of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
⁸ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
⁹ Centro de Astrobiología (CAB), CSIC-INTA, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain
¹⁰ I.Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
¹¹ DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark
¹² Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
¹³ Telespazio UK for the European Space Agency, ESAC, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Spain
¹⁴ School of Physics & Astronomy, Space Park Leicester, University of Leicester, 92 Corporation Road, Leicester LE4 5SP, UK
¹⁵ Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands
¹⁶ Centre for Extragalactic Astronomy, Durham University, South Road, Durham DH1 3LE, UK
¹⁷ University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, 1180 Vienna, Austria
¹⁸ Institute of Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Str 27, 8093 Zurich, Switzerland

^⋆ Corresponding author: lcostantin@cab.inta-csic.es

Received: 1 July 2024
Accepted: 6 May 2025

Abstract

Context. Thanks to decades of observations using the Hubble Space Telescope (HST), the structure of galaxies at redshift z>2 has been widely studied in the rest-frame ultraviolet regime, which traces recent star formation from young stellar populations. However, we still have little information about the spatial distribution of the older, more evolved stellar populations, constrained by the rest-frame infrared portion of the galaxies’ spectral energy distribution.

Aims. We present the morphological characterization of a sample of 49 massive galaxies (log(M_⋆/M_⊙)>9) at redshift 3<z<5. These galaxies are observed as part of the MIRI Deep Imaging Survey (MIDIS), the guaranteed time observations program with the MIRI instrument on board the James Webb Space Telescope (JWST). Deep MIRI 5.6 μm imaging (28.64 mag 5σ depth) allows us to characterize the rest-frame near-infrared structure of galaxies beyond cosmic noon, at higher redshifts than possible with NIRCam, tracing their older and dust-insensitive stellar populations.

Methods. We derived the nonparametric morphology of galaxies, focusing on the Gini, M₂₀, concentration, asymmetry, and deviation statistics. Furthermore, we modeled the light distribution of galaxies with a single Sérsic component and derived their parametric morphology (i.e., effective radius and Sérsic index).

Results. We find that at z>3 massive galaxies show a smooth distribution of their rest-infrared light, strongly supporting the increasing number of regular disk galaxies already in place at early epochs. These results are further reinforced by the analysis of JWST/NIRCam data at 4.4 μm. On the contrary, the ultraviolet structure obtained from HST/WFC3 and JWST/NIRCam observations at ∼1.5 μm is generally more irregular, catching the most recent episodes of star formation. Importantly, we find a segregation of morphologies across cosmic time, where galaxies at redshift z>3.75 show later-type morphologies compared to z∼3 galaxies. These findings suggest a transition phase in galaxy assembly and central mass build-up, which takes place already at z∼3−4.

Conclusions. The combined analysis of NIRCam and MIRI imaging datasets allows us to prove that the rest-frame near-infrared morphology of massive galaxies at cosmic noon is typical of compact disk galaxies with a smooth mass distribution.