A cosmology with the growing cosmological constant (CC) energy density is considered. The requirement of general covariance implies the time dependence of the gravitational constant G. Irrespectively of the exact functional form of the growth of the CC energy density, the universe ends in a de Sitter regime with a constant asymptotic Λ, but vanishing G. Although there is no divergence of the sc...

Gravitational self-interactions are assumed to be determined by the covariant derivative acting on the Riemann-Christoffel field strength. Once imposed on a metric theory, this Yang-Mills gauge constraint extends the equality of gravitational mass and inertial mass to compact bodies with non-negligible gravitational binding energy. Applied to generalized Brans-Dicke theories, it singles out one...

Globular clusters are gravitationally bound stellar systems containing on the order of 10 stars. Due to the high stellar densities in the cores of these cluster, close encounters and even physical collisions between stars are inevitable. These dynamical interactions can produce exotic types of single and binary stars that are extremely rare in the galactic field, but which may be important to t...

Subarcsecond infrared and radio observations yield important information about the formation of super star clusters from their surrounding gas. We discuss the general properties of ionized and molecular gas near young, forming SSCs, as illustrated by the prototypical young, forming super star cluster nebula in the dwarf galaxy NGC 5253. This super star cluster appears to have a gravitationally ...

The Local Group is a small galaxy cluster with the membership of 62 nearby galaxies including the Milky Way and M31. Although the Local Group has yet to be virialized, it interacts with the surrounding matter as one gravitationally bound system. To understand the formation and evolution of the Local Group as well as its member galaxies, it is important to reconstruct the gravitational potential...

Clusters of galaxies are large gravitationally bound systems which consist of several observable components: hundreds of galaxies, hot gas between the galaxies and sometimes relativistic particles. These components are emitting in different wavelengths from radio to X-rays. We show that the combination of observations at different frequencies and also theoretical models is giving now a comprehe...

We revisit the application of Modified Newtonian Dynamics (MOND) to galaxy clusters. We confront the high quality X-ray data for eight clusters of galaxies observed by the XMM-Newton satellite with the predictions of MOND. We obtain ratios of the Newtonian dynamical mass to the MOND mass of Md/Mm = 1.09 ± 0.08 at r ∼ 0.1 Rvir increasing to Md/Mm = 1.57± 0.24 in the outer parts (i.e r ∼ 0.5 Rvir...

— We consider low angular momentum, neutrino cooled accretion flows onto newborn black holes in the context of the collapsar model for long Gamma Ray Bursts, and find a considerable energy release for rotation rates lower than those usually considered. The efficiency for the transformation of gravitational binding energy into radiation is maximized when the equatorial angular momentum l0 ≃ 2rgc.

Three-dimensional simulations of the disk-halo interaction show the formation of a thick HI and HII gas disk with different scale heights. The thick HI disk prevents the disk gas from expanding freely upwards, unless some highly energetic event such as chimneys occurs, whereas the thick HII disk acts as a diskhalo interaction region from where the hot ionized gas flows freely into the halo. The...

WISE J104915.57−531906.1 is a L/T brown dwarf binary located 2 pc from the Sun. The pair contains the closest known brown dwarfs and is the third closest known system, stellar or sub-stellar. We report comprehensive follow-up observations of this newly uncovered system. We have determined the spectral types of both components (L8±1, for the primary, agreeing with the discovery paper; T1.5±2 for...