We investigate the regularity of cluster pressure profiles with REXCESS, a representative sample of 33 local (z < 0.2) clusters drawn from the REFLEX catalogue and observed with XMM-Newton. The sample spans a mass range of 10 14 M < M 500 < 10 15 M , where M 500 is the mass corresponding to a density contrast of 500. We derive an average profile from observations scaled by mass and redshift according to the standard self-similar model, and find that the dispersion about the mean is remarkably low, at less than 30 per cent beyond 0.2 R 500 , but increases towards the center. Deviations about the mean are related to both the mass and the thermo-dynamical state of the cluster. Morphologically disturbed systems have systematically shallower profiles while cooling core systems are more concentrated. The scaled profiles exhibit a residual mass dependence with a slope of ∼0.12, consistent with that expected from the empirically-derived slope of the M 500 − Y X relation; however, the departure from standard scaling decreases with radius and is consistent with zero at R 500 . The scatter in the core and departure from self-similar mass scaling is smaller compared to that of the entropy profiles, showing that the pressure is the quantity least affected by dynamical history and non-gravitational physics. Comparison with scaled data from several state of the art numerical simulations shows good agreement outside the core. Combining the observational data in the radial range [0.03−1] R 500 with simulation data in the radial range [1−4] R 500 , we derive a robust measure of the universal pressure profile, that, in an analytical form, defines the physical pressure profile of clusters as a function of mass and redshift up to the cluster "boundary". Using this profile and direct spherical integration of the observed pressure profiles, we estimate the integrated Compton parameter Y and investigate its scaling with M 500 and L X , the soft band X-ray luminosity. We consider both the spherically integrated quantity, Y sph (R), proportional to the gas thermal energy, and the cylindrically integrated quantity,A , which is directly related to the Sunyaev-Zel'dovich (SZ) effect signal. From the low scatter of the observed Y sph (R 500 )−Y X relation we show that variations in pressure profile shape do not introduce extra scatter into the Y sph (R 500 )− M 500 relation as compared to that from the Y X − M 500 relation. The Y sph (R 500 )− M 500 and Y sph (R 500 )−L X relations derived from the data are in excellent agreement with those expected from the universal profile. This profile is used to derive the expected Y SZ − M 500 and Y SZ − L X relations for any aperture.

We present the compilation and properties of a meta-catalogue of X-ray detected clusters of galaxies, the MCXC. This very large catalogue is based on publicly available ROSAT All Sky Survey-based (NORAS, REFLEX, BCS, SGP, NEP, MACS, and CIZA) and serendipitous (160SD, 400SD, SHARC, WARPS, and EMSS) cluster catalogues. Data have been systematically homogenised to an overdensity of 500, and duplicate entries from overlaps between the survey areas of the individual input catalogues are carefully handled. The MCXC comprises 1743 clusters with virtually no duplicate entries. For each cluster the MCXC provides three identifiers, a redshift, coordinates, membership in the original catalogue, and standardised 0.1−2.4 keV band luminosity L 500 , total mass M 500 , and radius R 500 . The meta-catalogue additionally furnishes information on overlaps between the input catalogues and the luminosity ratios when measurements from different surveys are available, and gives notes on individual objects. The MCXC is available in electronic format for maximum usefulness in X-ray, SZ, and other multiwavelength studies.