Related papers: Hidden BL Lacertae Objects Near and Far
It has been claimed that the standard model of cosmology (LCDM) cannot easily account for a number of observations on relatively small scales, motivating extensions to the standard model. Here we introduce a new suite of cosmological…
The HST snapshot imaging survey of 110 BL Lac objects (Urry et al. 2000) has clearly shown that the host galaxies are massive and luminous ellipticals. The dispersion of the absolute magnitudes is sufficiently small, so that the measurement…
Surveys with submillimetre telescopes are revealing large numbers of gravitationally lensed high-redshift sources. I describe how, in practice, these lensed systems could be simultaneously used to estimate the values of cosmological…
There are many observational evidences for the detection of compact objects with masses significantly larger (in galactic cases) or much larger (in extragalactic cases) than the upper limits of masses of em cold Neutron Stars. Such compact…
Observational evidence indicating that the expansion of the universe is accelerating has surprised cosmologists in recent years. Cosmological models have sought to explain this acceleration by incorporating `dark energy', of which the…
The evolution of the luminosity distance in a contracting universe is studied. It is shown that for quite a lot of natural dynamical evolutions, its behavior is far from trivial and its value can even decrease with an increasing time…
Massive stars are key ingredients in the evolution of the Universe. Yet, important uncertainties and limits persist in our understanding of these objects, even in their early phases, limiting their application as tools to interpret the…
So far, high resolution techniques on the one hand provide morphological information on bright nearby objects. On the other hand, telescopes with large collecting areas allow us to detect very faint and distant objects, but not to obtain a…
Recent studies have found a dramatic difference between the observed number density evolution of low mass galaxies and that predicted by semi-analytic models. While models accurately reproduce the z=0 number density, they require that the…
We study the evolution of LTB Universe models possessing a varying cosmological term and a material fluid.
This article reviews and discusses 1) the discovery and early work on the evolution of quasars and AGNs, 2) the different techniques used to find quasars and their suitability for evolutionary studies, 3) the current status of our knowledge…
The nearby galaxies of the Local Group can act as our laboratories in helping to bridge the gap between theory and observations. In this review we will describe the complications of identifying samples of OB stars, yellow and red…
This paper reviews the current status of measurements of galaxy clustering at high redshifts (z > 0.3). The focus is on the inherent limitations in the observation and interpretation of the ``evolution of clustering''. It is likely that…
The problem of error growth due to the incomplete knowledge of the evolution law which rules the dynamics of a given physical system is addressed. Major interest is devoted to the analysis of error amplification in systems with many…
Observations of galaxies over large distances reveal the possibility of a fractal distribution of their positions. The source of fractal behavior is the lack of a length scale in the two body gravitational interaction. However, even with…
A huge amount of good quality data converges towards the picture of a spatially flat universe undergoing the today observed phase of accelerated expansion. This new observational trend is commonly addressed as Precision Cosmology. Despite…
Many compact objects (black holes and neutron stars) exist in binaries. These binaries are normally discovered through their interactions, either from accretion as an X-ray binary or collisions as a gravitational wave source. However, the…
It is argued that some of the recent claims for cosmology are grossly overblown. Cosmology rests on a very small database: it suffers from many fundamental difficulties as a science (if it is a science at all) whilst observations of distant…
We present constraints on the cosmic growth history with recent cosmological data, allowing for deviations from Lambda CDM as might arise if cosmic acceleration is due to modifications to GR or inhomogeneous dark energy. We combine measures…
The discovery of cosmic acceleration is one of the most important developments in modern cosmology. The observation, thirteen years ago, that type Ia supernovae appear dimmer that they would have been in a decelerating universe followed by…