We make a case for the existence for ultra-massive black holes (UMBHs) in the Universe, but argue that there exists a likely upper limit to black hole masses of the order of M ∼ 1010M⊙. We show that there are three strong lines of argument that predicate the existence of UMBHs: (i) expected as a natural extension of the observed black hole mass bulge luminosity relation, when extrapolated to th...

We describe a new approach to constrain the amplitude of matter perturbations in the Universe using galaxy clusters. We combine the galaxy cluster X-ray luminosity function of the REFLEX survey with the mass– luminosity relationship obtained via gravitational lensing from a sample of galaxy clusters identified in Sloan Digital Sky Survey commissioning data and confirmed through cross-correlatio...

A 7.5 years spectrophotometric monitoring program of 28 Palomar-Green quasars to determine the size of their broad emission line region (BLR) is reviewed. We find both the continuum and the emission line fluxes of all quasars to vary during this period. Seventeen objects has adequate sampling for reverberation mapping and in all of them we find the Balmer line variations to lag those of the con...

We model the luminosity-dependent projected two-point correlation function of DEEP2 and SDSS galaxies within the Halo Occupation Distribution (HOD) framework. From this we infer the relationship between galaxy luminosity and host dark matter halo mass at z ∼ 1 and at z ∼ 0. At both epochs, there is a tight correlation between central galaxy luminosity and halo mass, with the slope and scatter d...

We present a statistical study of the occurrence and effects of the cooling cores in the clusters of galaxies in a flux-limited sample, HIFLUGCS, based on ROSAT and ASCA observations. About 49% of the clusters in this sample have a significant, classically-calculated cooling-flow, mass-deposition rate. The upper envelope of the derived mass-deposition rate is roughly proportional to the cluster...

Using Chandra X-ray observations and optical imaging and spectroscopy of a flux-limited sample of 5 fossil groups, supplemented by additional systems from the literature, we provide the first detailed study of the scaling properties of fossils compared to normal groups and clusters. Fossil groups are dominated by a single giant elliptical galaxy at the centre of an extended bright X-ray halo. I...

If dark halos are composed of dense gas clouds, as has recently been inferred, then collisions between clouds lead to galaxy evolution. Collisions introduce a core in an initially singular dark matter distribution, and can thus help to reconcile scale-free initial conditions – such as are found in simulations – with observed halos, which have cores. A pseudo-Tully-Fisher relation, between halo ...

Using results of Chandra observations of old stellar systems in eleven nearby galaxies of various morphological types and the census of LMXBs in the Milky Way, we study the population of low mass X-ray binaries and their relation to the mass of the host galaxy. We show that the azimuthally averaged spatial distribution of the number of LMXBs and, in the majority of cases, of their collective lu...

Using a simple description of feedback from black hole growth, we develop an analytic model for the fueling of Seyferts (low-luminosity AGN) and their relation to their host galaxies, Eddington ratio distributions, and cosmological evolution. We derive a solution for the time evolution of accretion rates in a feedback-driven blast wave, applicable to large-scale outflows from bright quasars in ...

The presence of a cool multicolor disk component with an inner disk temperature kT = 0.1 ∼ 0.3 keV at a luminosity L > 10 40 ergs s −1 has been interpreted as evidence that the ultraluminous X-ray source NGC 1313 X-2 harbors an intermediate-mass black hole (IMBH). The temperature of a disk component should vary with luminosity as L ∝ T 4. However, upon investigating the spectral evolution with ...