Calibration of the galaxy cluster M500-YX relation with XMM-Newton
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 1013 -1015 Msun keV, we investigate the M500-Y X relation. The M500 - Y X data exhibit a power law relation with slope alpha=0.548 0.027, close to the self-similar value (3/5) and independent of the mass range considered. However, the normalisation is 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 Mg,500.