We compare the B-band luminosity function of virialized halos with the mass function predicted by the Press-Schechter theory in cold dark matter cosmogonies. We find that all cosmological models fail to match our results if a constant mass–to–light ratio is assumed. In order for these models to match the faint end of the luminosity function, a mass–to–light ratio decreasing with luminosity as L...

Received ; accepted – 2 – ABSTRACT An origin is sought for the ubiquity of cusps, both in computer simulations of halo formation in hierarchical clustering cosmogonies and in observations of galactic nuclei by the Hubble Space Telescope (HST). The encounters of merging clumps that built the galaxies can be described by the collisional Boltzmann equation. Using insights gained by studying the si...

The origin and nature of Ultra-Luminous X-ray sources (ULXs) is a contentious and controversial topic. There are ongoing debates about the masses of the objects responsible, their sources of mass for accretion, and their relation to stellar populations in galaxies. A new picture of these objects is proposed in which they are intermediate-mass black holes confined to the disks of their host gala...

It has been observed that Cepheids in the Magellanic Clouds have lower masses for the same luminosity than those in the Milky Way. The model, from Neilson & Lester (2008), of pulsation– driven mass loss for Cepheids is applied to theoretical models of Cepheids with metallicity consistent with the Milky Way and Large and Small Magellanic Clouds. The mass–loss model is analyzed using the metallic...

We present an analysis of the color-magnitude-velocity dispersion relation for a sample of 39320 earlytype galaxies within the Sloan Digital Sky Survey. We demonstrate that the color-magnitude relation is entirely a consequence of the fact that both the luminosities and colors of these galaxies are correlated with stellar velocity dispersions. Previous studies of the color-magnitude relation ov...

Massive Black Holes detected in the centers of many nearby galaxies show an approximately linear relation with the luminosity of the host bulge, with the black hole mass being 0.001-0.002 of the bulge mass. Previous work suggested that black holes of active (Seyfert 1) galaxies follow a similar relation, but apparently with a significantly lower value of MBH/Mbulge (Wandel 1999). New data show ...

As a result of a systematic NIR H-band (1.65μm) imaging survey of normal galaxies in the local universe that includes objects both in the Virgo cluster and in the “Great Wall” (including A1367, A1656 as well as the “isolated” population in the bridge between the two clusters), we are able to measure in a highly homogeneous way photometric and structural properties for a sample of 1143 galaxies....

The presence of dilute hot cavities in the intracluster medium (ICM) at the cores of clusters of galaxies changes the relation between gas temperature and its X-ray emission properties. Using the hydrostatic equations of a porous medium we solve for the ICM density for a given temperature as a function of the filling factor of dilute bubbles. We find that at a given temperature, the core X-ray ...

We study the evolution of two fundamental properties of galaxy clusters: the luminosity function (LF) and the scaling relations between the total galaxy number N (or luminosity) and cluster mass M. Using a sample of 27 clusters (0 ≤ z ≤ 0.9) with new near-IR observations and mass estimates derived from X–ray temperatures, in conjunction with data from the literature, we construct the largest sa...

We show that the X-ray power density spectra do not simply scale linearly with the mass of the black hole over many decades. Nevertheless, the high frequency tail of the power density spectrum can be successfully used for determination of the black hole mass in an AGN if another AGN is used as a reference. We determine the masses of the black holes in 6 Broad Line Seyfert 1 galaxies, 5 Narrow L...