We present the first results from our spectroscopic survey of theenvironments of strong gravitational lenses.

We explore the possibility that galaxy clusters or halos could besuited environments to host fermions like massive neutrinos in theirdegenerate state. Equilibrium density profiles for galaxy clustersand halos are calculated where the contribution of fermion particlesto an isotropic collisionless component is taken into account.Fermions are supposed to cluster in CDM protoclusters while theirphase space density is sufficient for not neglecting the Pauli'sexclusion principle.


From a sample of more than 100 remnants from major and minor hydrodynamic binary galaxy merger simulations (Cox 2004; Cox et al. 2005), we find that stellar remnants are mostly oblate while dark matter halos are mostly prolate or triaxial. Shapes are determined by iteratively diagonalizing a moment-of-inertia tensor. The preferred axes of the two shapes are almost always nearly perpendicular. This can be understood by considering the influence of angular momentum and dissipation during the merger. If binary major mergers of spiral galaxies are responsible for the formation of elliptical galaxies or some subpopulation of elliptical galaxies, then the galaxies can be be expected to be oblate and the dark matter halos prolate with the two preferred axes perpendicular to each other.

We examine the systematics affecting the X-ray mass estimators applied toChandra-like long exposures images of five simulated clusters.

We have developed an analytic model for a preheated, polytropic IGM inhydrostatic equilibrium within a NFW potential in which the evolutionof the halo structure between major merger events proceeds inside-outby accretion. For a polytropic index of 1.2, consistent with both manyobservational results and predictions from high-resolution gasdynamicalsimulations, our model is capable of reproducing faithfully all theobserved X-ray properties of nearby relaxed, non-cooling flow groupsand clusters of galaxies with a universal level of energy injection ofabout half a keV (see Solanes et al. 2005 for details).

We review briefly results presented in Tasitsiomi, Kravtsov, Gottloeber and Klypin, ApJ 607, 125 (2004).

Using cosmological N-body simulations we study theline-of-sight velocity distribution of dark matterhaloes focusing on the lowest-order even moments,dispersion and kurtosis, and their application toestimate the mass profiles of cosmological structures.For each of the ten massive haloes selected from the simulation boxwe determine the virial mass, concentration and the anisotropy parameter.In order to emulate observations from each halo we choose randomly 300 particlesand project their velocities and positions along the line of sight and on the surfaceof the sky, respectively. After removing interlopers we calculate the profiles of the line-of-sightvelocity moments and fit them with the solutions of the Jeans equations.The estimates of virial mass, concentration parameter and velocity anisotropyobtained in this way are in good agreement with the values found from the full 3D analysis.

Faber–Jackson and Tully–Fisher scaling relations forelliptical and spiral galaxy samples up to z = 1provide evidence for a differential behaviour of galaxy evolution with mass.In compliance with the downsizing scenario, the stellar populations of lessmassive galaxies display a stronger evolution than the more massive ones.For spirals, this may be attributed to a suppressed star formation efficiencyin small dark matter halos.For ellipticals, star formation must have been negligible at leastduring the past ~4 Gyr in all environments.