Related papers: An evolutionary model for GHz Peaked Spectrum Sour…

Gigahertz Peaked Spectrum (GPS) sources form a key element in the study of the onset and evolution of radio-loud AGN, since they are most likely the young counterparts of extended radio sources. Here we discuss space-VLBI observations of…

I review some recent cosmological studies based on redshift surveys of radio sources selected at low frequencies. The accretion rate onto the central black hole is identified as the basis of a crude physical division of the low-frequency…

The compact steep spectrum (CSS) and gigahertz peaked spectrum (GPS) sources are widely believed to be young radiosources, with ages <10^6 yr. If the activity in the nucleus is fuelled by the supply of gas, one might find evidence of this…

I derive and discuss a simple semi-analytical model of the evolution of powerful radio galaxies which is not based on assumptions of self-similar growth, but rather implements some insights about the dynamics and energetics of these systems…

Deep optical images have been gathered for a nearly complete sample of radio galaxies from the Revised 3rd Cambridge (3CR) Catalog in the redshift range 0.15 < z < 0.65. Total and nuclear magnitudes and colors have been extracted. The…

We used the Australia Telescope Compact Array (ATCA) to obtain 40 GHz and 95 GHz observations of a number of sources that were selected from the Australia Telescope Compact Array 20 GHz (AT20G) survey . The aim of the observations was to…

High-redshift quasars are important to study galaxy and active galactic nuclei (AGN) evolution, test cosmological models, and study supermassive black hole growth. Optical searches for high-redshift sources have been very successful, but…

We explore the radio properties of powerful (rest-frame luminosity $\gtrsim10^{28}$ W Hz$^{-1}$ at 500 MHz) high-redshift (z > 3.5) quasars. The aim of this study is to gain a better understanding of radio-loud sources at the epoch when…

In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-Peaked-Spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population…

Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources are compact radio galaxies (RGs), with jets extending up to 20 kpc and ages <10^3 years. They are considered to evolve to Fanaroff-Riley RGs, but the real scenario to…

We consider the high radio frequency (15 GHz - 353 GHz) properties and variability of 35 Brightest Cluster Galaxies (BCGs). These are the most core-dominated sources drawn from a parent sample of more than 700 X-ray selected clusters, thus…

According to the currently accepted paradigm compact steep spectrum (CSS) sources are precursors of larger/older objects and gigahertz peaked spectrum (GPS) sources may be earlier stages of CSS sources. In this paper we confront this…

We consider the incidence of HI absorption in intrinsically small sub-galactic sized extragalactic sources selected from sources classified as Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources. We find that the…

A sample of high-frequency peaker (HFP) candidates was formed from the AT20G catalog radio sources with spectral indices of the optically thick emission region $\alpha_{below}$ exceeding +0.5. A study of the spectral properties of the…

We discuss our ATCA 18.5 and 22 GHz flux density measurements of the Southern extragalactic sources in the complete 5-GHz sample of Kuehr et al. (1981). The high-frequency (5-18.5 GHz) spectral indices of steep-spectrum sources for which we…

Spectroscopic observations of a sample of 42 flat-spectrum radio sources from the Cosmic Lens All-Sky Survey (CLASS) have yielded a mean redshift of $<z> = 1.27$ with an RMS spread of 0.95, at a completeness level of 64%. The sample…

Many of the powerful radio galaxies observed at high redshift are very small, presumably because they are very young. A simple model, which treats the radio source as a bubble expanding into a radially stratified medium, is capable of…

The evolutionary stage of a powerful radio source originated by an AGN is related to its linear size. In this context, compact symmetric objects (CSOs), which are powerful and intrinsically small (< 1 kpc) radio sources with a convex…

We study the morphology of the radio emission of giant radio galaxies (GRGs), a rare type of active galaxies, in order to find new clues for the reasons of their large size. Using radio images from two sky surveys at 1.4 GHz we quantified…

The origin of the radio emission in radio-quiet quasars (RQQs) remains unclear. Radio emission may be produced by a scaled-down version of the relativistic jets observed in radio-loud (RL) AGN, an AGN-driven wind, the accretion disc corona,…