Volume 474, Number 3, November II 2007
|Page(s)||L37 - L40|
|Published online||23 October 2007|
Letter to the Editor
Calibration of the galaxy cluster M500–Y relation with XMM-Newton
Laboratoire AIM, DAPNIA/Service d'Astrophysique - CEA/DSM - CNRS - Université Paris Diderot, Bât. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France e-mail: Monique.Arnaud@cea.fr
2 CESR, 9 Av. du colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
3 Max-Planck-Institut für extraterrestriche Physik, Giessenbachstraße, 85748 Garching, Germany
Accepted: 9 September 2007
The quantity YX, the product of the X-ray temperature TX and gas mass Mg, 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 YX range of 1013–1015 keV, we investigate the M500–YX relation. The M500–YX data exhibit a power law relation with slope α = 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 hydrostatic equilibrium 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 YX may indeed be a better mass proxy than TX or Mg,500.
Key words: cosmology: observations / cosmology: dark matter / galaxies: clusters: general / galaxies: intergalactic medium / X-rays: galaxies: clusters
© ESO, 2007
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