Calibration of the galaxy cluster M_500-Y_X relation with XMM-Newton

TL;DR

This study calibrates the M_500-Y_X relation using XMM-Newton data for relaxed galaxy clusters, finding a power law relation close to theoretical predictions but with a normalization offset, and suggesting Y_X as a superior mass proxy.

Contribution

The paper provides the first precise calibration of the M_500-Y_X relation with XMM-Newton data, highlighting its robustness and potential as a mass proxy for galaxy clusters.

Findings

Power law relation with slope ~0.55, close to self-similar prediction.

Normalization is about 20% below simulation predictions.

Y_X may be a better mass proxy than T_X or M_g,500.

Abstract

The quantity Y_ X, the product of the X-ray temperature T_ X and gas mass M_ g, has recently been proposed as a robust low-scatter mass indicator for galaxy clusters. Using precise measurements from XMM-Newton data of a sample of 10 relaxed nearby clusters, spanning a Y_ X range of 10^13 -10^15 M_sun keV, we investigate the M_500-Y_ X relation. The M_500 - Y_ X data exhibit a power law relation with slope alpha=0.548 \pm 0.027, close to the self-similar value (3/5) and independent of the mass range considered. However, the normalisation is \sim 20% below the prediction from numerical simulations including cooling and galaxy feedback. We discuss two effects that could contribute to the normalisation offset: an underestimate of the true mass due to the HE assumption used in X-ray mass estimates, and an underestimate of the hot gas mass fraction in the simulations. A comparison of the functional form and scatter of the relations between various observables and the mass suggest that Y_ X may indeed be a better mass proxy than T_ X or M_g,500.