We propose a new interpretation of the quasar luminosity function (LF), derived from physically motivated models of quasar lifetimes and light curves. In our picture, quasars evolve rapidly and their lifetime depends on both their instantaneous and peak luminosities. We study this model using simulations of galaxy mergers that successfully reproduce a wide range of observed quasar phenomena. Wi...

Using the results of recent optical surveys we conclude that the non-detection of quasars down to faint magnitudes implies a significant flattening of the high redshift (z ∼ 6) optical active galactic nuclei (AGN) luminosity function for M1450 > −26.7. We find that all the data are consistent with a faint-end slope for the optical AGN luminosity function of β = −2.2 and β = −2.8, at the 90% and...

We report a 3σ upper limit of 220μJy on any 22-GHz continuum emission coincident with the central engine in NGC 4258. If NGC 4258 is powered by an advection-dominated accretion flow, this radio upper limit implies that the inner advection-dominated flow cannot extend significantly beyond ∼ 10 Schwarzschild radii. Subject headings: accretion, accretion disks — galaxies: active — galaxies: nuclei...

The deep near–infrared luminosity function of AC118, a cluster of galaxies at z = 0.3, is presented. AC118 is a bimodal cluster, as evidenced both by our near–infrared images of lensed galaxies, by public X–ray Rosat images and by the spatial distribution of bright galaxies. Taking advantage of the extension and depth of our data, which sample an almost unexplored region in the depth vs. observ...

Deep X–ray surveys are providing crucial information on the evolution of AGN and galaxies. We review some of the latest results based on the X–ray spectral analysis of the sources detected in the Chandra Deep Field South, namely: i) constraints on obscured accretion; ii) constraints on the missing fraction of the X–ray background; iii) the redshift distribution of Compton–thick sources and Type...

We present the discovery of a high-redshift, X-ray–selected active galactic nucleus (AGN) by the Calan-Yale Deep Extragalactic Research (CYDER) survey: CXOCY J033716.7 050153, located at z 1⁄4 4:61, the second high-redshift AGN discovered by this survey. Here we present its optical, near-IR, and X-ray properties and compare it with other optical and X-ray–selected high-redshift AGNs. The optica...

The galaxy central mass Mc and central velocity dispersion σc have been found to correlate with large scale galaxy parameters for samples of galaxies with a limited range of characteristics. A scalar potential model (SPM) that derived from considerations of galaxy clusters, of redshift, of discrete redshift, of HI rotation curves (RCs) of spiral galaxies and of RC asymmetry is applied to centra...

Recent observational results obtained with SCUBA, COBE and ISO have greatly improved our knowledge of the infrared and sub-mm background radiation. These limits become constraining given the realization that most AGNs are heavily obscured and must reradiate strongly in the IR/sub-mm. Here we predict the contribution of AGNs to the IR/sub-mm background, starting from measurements of the hard X-r...

We report the result of an on-going survey for 22 GHz H2O maser emission towards infrared luminous galaxies. The observed galaxies were selected primarily from the IRAS bright galaxy sample. The survey has resulted in the detection of one new maser. The new maser was discovered towards the [U]LIRG/merger galaxy NGC6240, which contains a LINER nucleus. This is the first detection of an H2O maser...

Historically, Seyfert nuclei have been considered to be radio-quiet active galactic nuclei (AGNs). We question this widely held assumption by showing that the distribution of the radio-to-optical luminosity ratio, R ≡ Lν(6 cm)/Lν(B), when properly measured for the nuclear component, places the majority of type 1 Seyfert nuclei in the category of radio-loud AGNs, defined here as objects with R ≥...