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We simulate the formation of a large X-ray cluster using a fully 3D hydrodynamical code coupled to a Particle-Mesh scheme which models the dark matter component. We focus on a possible decoupling between electrons and ions temperatures. We then solve the energy transfer equations between electrons, ions and neutrals without assuming thermal equilibrium between the three gases (T_e <> T_i <> T_n). We solve self-consistently the chemical equations for an hydrogen/helium primordial plasma without assuming ionization-recombination equilibrium. We find that the electron temperature differs from the true dynamical temperature by 20% at the Virial radius of our simulated cluster. This could lead marginally to an underestimate of the total mass in the outer regions of large X-ray clusters.
$renewcommand{Re}{mathbb{R}}$Given a set $P$ of $n$ points in $Re^d$, consider the problem of computing $k$ subsets of $P$ that form clusters that are well-separated from each other, and each of them is large (cardinality wise). We provide tight uppe
We present first strong observational evidence that the X-ray cool-core bias or the apparent bias in the abundance of relaxed clusters is absent in our REFLEX volume-limited sample (ReVols). We show that these previously observed biases are due to th
Self-synchronization is a ubiquitous phenomenon in nature, in which oscillators are collectively locked in frequency and phase through mutual interactions. While self-synchronization requires the forced excitation of at least one of the oscillators,
A recent study has presented marginal statistical evidence that gamma-ray burst sources are correlated with Abell clusters, based on analyses of bursts in the BATSE 3B catalog. Using precise localization information from the 3rd Interplanetary Networ
We report on the first results from a redshift survey of a flux-limited sample of X-ray clusters selected serendipitously from the ROSAT PSPC data archive. We spectroscopically confirm 15 clusters in the range 0.3 < z < 0.7, to a flux limit of ~ 3.9