We present a new accurate measurement of the H I mass function of galaxies from the HIPASS Bright Galaxy Catalog, a sample of 1000 galaxies with the highest H I peak flux densities in the southern (δ < 0) hemisphere (Koribalski et al. 2003). This sample spans nearly four orders of magnitude in H I mass (from log(MHI⁄ M⊙) + 2logh75 = 6.8 to 10.6) and is the largest sample of H I selected galaxie...

In our search for “hidden” AGN we present results from a Chandra observation of the nearby cluster Abell 2255. Eight cluster galaxies are associated with point-like X-ray emission, and we classify these galaxies based on their X-ray, radio, and optical properties. At least three are associated with active galactic nuclei (AGN) with no optical signatures of nuclear activity, with a further two b...

Using deep Hubble Space Telescope Advanced Camera for Surveys imaging and Very Large Telescope FOcal Reducer/low dispersion Spectrograph 2 spectra, we determined the velocity dispersions, effective radii, and surface brightnesses for four early-type galaxies in the cluster RDCS 1252.9 2927. All four galaxies are massive, z p 1.237 greater than . These four galaxies, combined with three from RDC...

Seyfert nuclei are typical active galactic nuclei (AGNs) in the local universe, which are thought to be powered by gas accretion onto a supermassive black hole (SMBH). The dynamical effect exerted either by non-axisymmetric gravitational potential (such as a stellar bar) or by interaction with other galaxies has been often considered to cause the efficient gas fueling. However, recent systemati...

A novel statistic is proposed to examine the hypothesis that all cluster galaxies are drawn from the same luminosity distribution (LD). In such a “statistical model” of galaxy LD, the brightest cluster galaxies (BCGs) are simply the statistical extreme of the galaxy population. Using a large sample of nearby clusters, we show that BCGs in high luminosity clusters (e.g., Ltot & 4× 1011h−2 70L⊙) ...

We derive a viscosity from gravitational instability in self-gravitating accretion disks, which has the required properties to account for the observed fast formation of the first super-massive black holes in highly redshifted quasars and for the cosmological evolution of the black hole-mass distribution. Subject headings: accretion, accretion disks — hydrodynamics — turbulence — galaxies: acti...

We analyse the B−Rc colors of galaxies as functions of luminosity and local galaxy density using a large photometric redshift catalog based on the Red-Sequence Cluster Survey. We select two samples of galaxies with a magnitude limit ofMRc < −18.5 and redshift ranges of 0.2 ≤ z < 0.4 and 0.4 ≤ z < 0.6 containing ∼ 10 galaxies each. We model the color distributions of subsamples of galaxies and d...

We present evidence for a significant overdensity of red galaxies, as much as a factor of 14 over comparable field samples, in the field of the z = 1.47 radio galaxy B3 0003+387. The colors and luminosities of the brightest red galaxies are consistent with their being at z > 0.8. The radio galaxy and one of the red galaxies are separated by 5 and show some evidence of a possible interaction. Ho...

The effect of redshift on the observation of distant galaxies is briefly discussed emphasizing the possible sources of bias in the interpretation of high-z data. A general energetic criterion to assess physical self-consistency of evolutionary population synthesis models is also proposed, for a more appropriate use of this important tool to investigate distinctive properties of primeval galaxies.

A simple model is constructed to evaluate the change of star formation rate of a disk galaxy due to environmental e†ects in clusters of galaxies. Three e†ects are investigated : (1) tidal force from the potential well of the cluster, (2) increase of external pressure when the galaxy plows into the intracluster medium, and (3) high-speed encounters between galaxies. General analysis indicates th...