Letter to the Editor

The impact of strong feedback on galaxy group scaling relations

¹ Department of Astronomy, University of Geneva, Ch. d’Ecogia 16, 1290, Versoix, Switzerland
² Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg, Germany
³ Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2, 00560, Helsinki, Finland
⁴ INAF – IASF Milano, Via Alfonso Corti 12, 20133, Milan, Italy
⁵ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA, 02138, USA
⁶ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via P. Gobetti 93/3, 40129, Bologna, Italy
⁷ INFN, Sezione di Bologna, Viale Berti Pichat 6/2, 40127, Bologna, Italy
⁸ CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO, 80309, USA
⁹ Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, UK
¹⁰ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
¹¹ Department of Physics and Astronomy, University of Alabama in Huntsville, Huntsville, AL, 35899, USA
¹² Department of Computer Science, Aalto University, PO Box 15400, Espoo, FI-00 076, Finland
¹³ Departamento de Física Teórica, M-8, Universidad Autónoma de Madrid, Cantoblanco, E-28049, Madrid, Spain
¹⁴ Centro de Investigación Avanzada en Física Fundamental (CIAFF), Universidad Autónoma de Madrid, Cantoblanco, E-28049, Madrid, Spain
¹⁵ Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ, United Kingdom
¹⁶ Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, PO Box 94, Makhanda, 6140, South Africa
¹⁷ South African Radio Astronomy Observatory, Black River Park North, 2 Fir St, Cape Town, 7925, South Africa
¹⁸ School of Physics and Astronomy, University of Birmingham, Birmingham, B152TT, UK

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

Received: 1 December 2025
Accepted: 14 March 2026

Abstract

Feedback from active supermassive black holes alters the distribution of matter in the Universe by injecting energy in the neighbouring hot gaseous medium, which leads to ejection of gas from the halos of galaxy groups and massive galaxies. Recent cosmological simulations such as FLAMINGO calibrate their feedback model on the baryon fractions of galaxy groups to tune the efficiency of gas ejection. However, recent observational constraints from optically selected groups and the kinetic Sunyaev–Zel’dovich effect yield lower baryon fractions than previous studies, which indicates that feedback may be more ejective than previously thought. In this work, we confirm that the scaling relations of local galaxy groups in the mass range 10¹³ − 10¹⁴ M_⊙ favour the fiducial FLAMINGO feedback calibration. We study the X-ray luminosity–temperature relation in a sample of 44 galaxy groups with high-quality XMM-Newton observations. We show that highly ejective models under-predict the luminosity of galaxy groups at fixed mass at high significance (5.7σ). This discrepancy cannot be explained by selection effects and is obtained from directly measurable and minimally correlated quantities. We point out that turning observable quantities into gas fraction estimates is challenging, especially in the context of stacking large samples of heterogeneous systems. We argue that validating feedback models against observable scaling relations is necessary to warrant the validity of feedback implementations in cosmological simulations.