In the local universe, most QSO absorption-lines seem to arise from gas in extended 100 kpc halos around spiral galaxies. We present evidence that at high redshift, at least some absorption lines come from diierent sources: the gas is associated not with spiral galaxy halos but with the intra-cluster medium of proto-galaxy clusters. This gas, which is neutral and lumpy, may form a true intra-cl...

Context. Extended gamma-ray emission, interpreted as halos formed by the inverse-Compton scattering of ambient photons electron-positron pairs, is observed toward a number middle-aged pulsars. The physical origin and actual commonness phenomenon in Galaxy remain unclear. conditions pair confinement seem extreme compared to what can be achieved recent theoretical models. Aims. We searched for sc...

Gravitational lensing is one of a number of methods used to probe the distribution of dark mass in the Universe. On galactic scales, complementary techniques include the use of stellar kinematics, kinematics and morphology of the neutral gas layer, kinematics of satellites, and morphology and temperature profile of X-ray halos. These methods are compared, with emphasis on their relative strengt...

Black hole formation is an inevitable consequence of relativistic core collapse following the gravothermal catastrophe in self-interacting dark matter (SIDM) halos. Very massive SIDM halos form supermassive black holes (SMBHs) > or about 10(6)M(middle dot in circle) directly. Smaller halos believed to form by redshift z = 5 produce seed black holes of (10(2)-10(3))M(middle dot in circle) which ...

We describe our recent attempts to model substructure in dark matter halos down to very small masses, using a semi-analytic model of halo formation. The results suggest that numerical simulations of halo formation may still be missing substructure in the central regions of halos due to purely numerical effects. If confirmed, this central 'overmerging' problem will have important consequences fo...

We study whether gravitational scattering of halo dark matter particles by subhalos can connect two seemingly independent problems: the abundance of subhalos in dark matter halos and the cuspiness of the halos' inner density profiles. Our numerical experiments indicate that subhalos can cause the collisionless dark matter particles in the centers of main halos to diffuse. Combined with tidal ma...

Phase contrast microscopy is widely used for live cell imaging. Automatic computer processing of phase-contrast images is complicated, particularly because of the halos that are present around the cells. We introduce a new algorithm able to segment individual cells by using the halos. The halos between cells are detected by thresholding and skeletonization, and gaps in the edges are filled in u...

We use a large set of state-of-the-art cosmological N-body simulations [512 particles] to study the intrinsic ellipticity correlation functions of halos. With the simulations of different resolutions, we find that the ellipticity correlations converge once the halos have more than 160 members. For halos with fewer members, the correlations are underestimated, and the underestimation amounts to ...