Evolution of the infrared luminosity function and its corresponding dust-obscured star formation rate density out to z  ∼  6

¹ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University Grudzidzka 5 87-100 Toruń, Poland
² Institute for Astronomy, University of Edinburgh, Royal Observatory Edinburgh EH9 3HJ, UK
³ Astronomical Observatory Institute, Faculty of Physics and Astronomy, Adam Mickiewicz University ul. Słoneczna 36 60-286 Poznań, Poland
⁴ National Centre for Nuclear Research Pasteura 7 093 Warsaw, Poland

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Received: 1 October 2025
Accepted: 3 January 2026

Abstract

We present a new determination of the evolving far-infrared (FIR) galaxy luminosity function (LF) and the resulting inferred evolution of dust-obscured star-formation rate density (ρ_SFR) out to redshift z ∼ 6. To establish the evolving comoving number density of FIR-bright objects, we made use of AS2UDS, a high-resolution ALMA follow-up study of the JCMT SCUBA-2 Cosmology Legacy Survey (S2CLS) submilliter imaging in the UKIDSS UDS survey field. In order to estimate the contributions of faint and low-mass sources, we implemented a method in which the faint-end of the IR LF is inferred by stacking (in stellar mass and redshift bins) the optical and near-infrared samples of star-forming galaxies into the appropriate FIR Herschel and submillimeter JCMT maps. Using this information we determined the faint-end slope of the FIR LF in two intermediate redshift bins (where it can be robustly established) and then adopted this result at all other redshifts. The evolution of the characteristic luminosity of the galaxy FIR LF, L_★, is found to increase monotonically with redshift, evolving as L_★ ∝ z^{1.38 ± 0.07}, while the characteristic number density, Φ_★, is well fit by a double power-law function; it is constant at z < 2.24 and declines as z^{−4.95 ± 0.73} at higher redshifts. We then calculated the evolution of the corresponding dust-obscured star-formation rate density and compared it with the results from a number of recent studies in the literature. Our analysis confirms that dust-obscured star formation activity dominates ρ_SFR at cosmic noon but then becomes progressively less important with increasing redshift. While dusty star-forming galaxies are still found out to the highest redshifts explored here, UV-visible star formation dominates at z > 4, and dust-obscured activity contributes less than 25% to the star formation rate density by z ∼ 6.