Astronomy and Astrophysics, volume 348, 711-727 (1999/8-3)
Regularity in the X-ray surface brightness profiles of galaxy clusters and the M-T relation.
NEUMANN D.M. and ARNAUD M.
Abstract (from CDS):
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<z<0.06. For 15 of these clusters accurate temperatures (kTX > 3.5keV) were available from the literature. The scaled emission measure profiles look remarkably similar above ∼0.2 times the virial radius (rVT200). On the other hand a large scatter is observed in the cluster core properties. We fitted a β-model (with and without excising the central part) to all the ROSAT profiles to quantify the structural variations in the cluster population, unraveling a robust quadratic correlation between the core radius and the slope parameter β. We quantified the shape of each gas density profile by the variation with radius of the logarithmic slope, αn. The bi-weight dispersion of αn 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 correlation between core radius and β. 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 αn 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 ∼3.5keV. Our results are consistent with the classical scaling relation between Mass and Temperature (M∝T3/2(1+z)–3/2). Accordingly the spread in the scaled mass profiles derived from the hydrostatic isothermal β-model is small. The very large scatter observed in the core properties favor scenario where Cooling Flows are periodically erased by merger events.
galaxies: clusters: general - cosmology: observations - cosmology: dark matter - X-rays: galaxies