Showing papers by "Monique Arnaud published in 1999"

Regularity in the X-ray surface brightness profiles of galaxy clusters and the M-T relation

Abstract: We used archival ROSAT observations to investigate the X-ray surface brightness profiles of a sample of 26 clusters in the redshift range 0:04 3:5 keV) were available from the literature. The scaled emission measure profiles look remark- ably similar above 0:2 times the virial radius (rVT200). On the other hand a large scatter is observed in the cluster core proper- ties. We fitted a -model (with and without excising the central part) to all the ROSAT profiles to quantify the structural vari- ations in the cluster population, unraveling a robust quadratic correlation between the core radius and the slope parameter . We quantified the shape of each gas density profile by the vari- ation with radius of the logarithmic slope, n. The bi-weight dispersion of n among the clusters is less than 20% for any given scaled radii above x =0 :2. There is a clear minimum spread at x =0 :3, which is related to the existence of a correla- tion between core radius and . These ensemble properties are insensitive to the exact treatment of a possible central excess when fitting the profiles. On the other hand the scatter in n is decreased when the radii are scaled to rVT200. The regularity we found in the gas profiles at x> 0:2 supports the existence of a universal underlying dark matter profile, as already predicted by theoretical works. It suggests that non gravitational heating is negligible for clusters with temperature above 3:5 keV. Our results are consistent with the classical scaling relation between Mass and Temperature (M / T 3=2 (1+ z) 3=2 ). Accordingly the spread in the scaled mass profiles derived from the hydrostatic isothermal -model is small. The very large scatter observed in the core properties favor scenario where Cooling Flows are periodically erased by merger events.