The impact of strong feedback on galaxy group scaling relations

TL;DR

This study examines how different feedback models affect galaxy group properties, finding that highly ejective feedback models are inconsistent with observed X-ray scaling relations in galaxy groups.

Contribution

It demonstrates that feedback models calibrated solely on baryon fractions are incompatible with observed galaxy group scaling relations, emphasizing the importance of using observable relations for calibration.

Findings

Highly ejective feedback models under-predict galaxy group luminosities at fixed mass.

Observable scaling relations provide more reliable calibration than baryon fraction measurements.

Results are robust against selection effects and measurement uncertainties.

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. Here we show that models involving highly ejective feedback are inconsistent with the scaling relations of local galaxy groups in the mass range $10^{13}-10^{14}M_\odot$. 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 ($5.7\sigma$). This conclusion is robust against 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 calibrating feedback models on baryon fractions is prone to systematic uncertainties and that observable scaling relations are better suited for this task.