The mean intracluster gas fraction of X–ray clusters within their hydrostatic regions is derived from recent observational compilations of David, Jones & Forman and White & Fabian. At radii encompassing a mean density 500 times the critical value, the individual sample bi-weight means are moderately (2.4σ) discrepant; revising binding masses with a virial relation calibrated by numerical simula...

This work is motivated by the following question: given a sample of compositional data trajectories (i.e. sequences of composition measurements along a domain), how can one propose a segmentation procedure leading to homogeneous classes? In other words, our contribution aims at studying statistical methods suited for clustering compositional data, when the observations are constituted by trajec...

Several arguments suggest that quasars at z > 4 may be in the cores of future giant ellipticals, and forming at the very highest peaks of the primordial density field. A strong bias-driven primordial clustering is then expected in these fields, which are naturally interpreted as the cores of future rich clusters. High-redshift quasars can thus be used as markers of some of the earliest galaxy f...

In hierarchical models, density fluctuations on different scales are correlated. This induces correlations between dark halo masses, their formation histories, and their larger-scale environments. In turn, this produces a correlation between galaxy properties and environment. This correlation is entirely statistical in nature. We show how the observed clustering of galaxies can be used to quant...

In this study we apply hierarchical spectral partitioning of bipartite graphs to a Dutch dialect dataset to cluster dialect varieties and determine the concomitant sound correspondences. An important advantage of this clustering method over other dialectometric methods is that the linguistic basis is simultaneously determined, bridging the gap between traditional and quantitative dialectology. ...