Related papers: The Great Attractor and the Shapley Concentration
We present an analysis of the velocity space of a sample of globular clusters (GC) with absolute proper motions. The vertical component of the velocity is found to be correlated with luminosity and galactocentric radius. We divided the…
This work studies a simplified model of the gravitational instability of an initially homogeneous infinite medium, represented by $\TT^d$, based on the approximation that the mean fluid velocity is always proportional to the local…
We study an aggregation PDE with competing attractive and repulsive forces on a sphere of arbitrary dimension. In particular, we consider the limit of strongly localized repulsion with a constant attraction term. We prove convergence of…
Relativistic jets of radio loud active galactic nuclei (AGN) produce highly directed, intense beams of radiation. A fraction of this beamed radiation scatters on the thermal plasma generally surrounding an AGN. The morphology of the…
Using archival data, we have made an HI absorption study of the 7$^\prime$ halo surrounding the Sgr A complex, observed towards the Galactic centre (GC) region. We find strong HI absorption near velocities of $-$53 km s$^{-1}$, which is due…
We consider scalar-tensor theories of gravity in an accelerating universe. The equations for the background evolution and the perturbations are given in full generality for any parametrization of the Lagrangian, and we stress that apparent…
Analysis of the peculiar velocities of galaxies should take account of the uncertainties in both redshifts and distances. We show how this can be done by a numerical application of the action principle. The method is applied to an improved…
We consider the consequences of applying general relativity to the description of the dynamics of a galaxy, given the observed flattened rotation curves. The galaxy is modeled as a stationary axially symmetric pressure-free fluid. In spite…
Two dozens of different mass galaxies observed at distances less than 10 Mpc from the Local Group are organized in the elongated structure known as the Sculptor Filament. We use recent Hubble Space Telescope data on local galaxies to study…
The dynamics of isolated galaxy pairs represents an important tool to investigate the behavior of gravity in the low acceleration regime. Statistical analysis of a large sample of galaxy pairs led to the noticeable discovery of a region of…
We tentatively look at anthropic constraints on the Cosmological Constant (CC) \Lambda at galactic scales by investigating its influence on the motion of the Sun throughout the Milky Way (MW) for -4.5 <= t <=0 Gyr. In particular, we look at…
Einstein's relation E=Mc^2 between the energy E and the mass M is the cornerstone of the relativity theory. This relation is often derived in a context of the relativistic theory for closed systems which do not accelerate. By contrast,…
We tackle the problem of the accelerating universe by reconsidering the most general form of the metric when the speed of light is allowed to evolve with time in a homogeneous and isotropic universe. A new varying speed of light (VSL) model…
Mass and concentration of clusters of galaxies are related and evolving with redshift. We study the properties of a sample of 31 massive galaxy clusters at high redshift, 0.8 < z < 1.5, using weak and strong lensing observations.…
We present significantly improved measurements of turbulent velocities in the hot gaseous halos of nearby giant elliptical galaxies. Using deep XMM-Newton Reflection Grating Spectrometer (RGS ) observations and a combination of resonance…
If modified gravity holds, but the weak lensing analysis is done in the standard way, one finds that dark matter halos have peculiar shapes, not following the standard Navarro-Frenk-White profiles, and are fully predictable from the…
We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly-magnified, ring-shaped configuration of four…
It is well known that the solar gravitational field can be considered as a telescope with a prime focus at locations beyond 550 au. In this work we present a new derivation of the wave-optical properties of the system, by adapting the…
The detailed nature of dark energy remains a mystery, leaving the possibility that its effects might be explained by changes to the laws of gravity on large scales. The peculiar velocities of galaxies directly trace the strength of gravity…
We analyze a sample of 23 supermassive elliptical galaxies (central velocity dispersion larger than 330 km s-1), drawn from the SDSS. For each object, we estimate the dynamical mass from the light profile and central velocity dispersion,…