The occurrence of Seyfert galaxies in 6 samples representative of different cosmological environments (i.e. isolated pairs, compact and loose groups) is analysed. To avoid biases linked to subjective sample selection criteria only canonical samples, taken from the literature, are considered. It is found that the average frequency of Seyferts in all samples, is near 2%. Most Seyferts lying in pa...

We use a complete sample of about 140,000 galaxies from the Sloan Digital Sky Survey (SDSS) to study the size distribution of galaxies and its dependence on their luminosity, stellar mass, and morphological type. The large SDSS database provides statistics of unprecedented accuracy. For each type of galaxy, the size distribution at given luminosity (or stellar mass) is well described by a log-n...

Aims. We investigate the cosmological evolution of largeand small-scale magnetic fields in galaxies in the light of present models of formation and evolution of galaxies. Methods. We use the dynamo theory to derive the timescales of amplification and ordering of magnetic fields in disk and puffy galaxies. Turbulence in protogalactic halos generated by thermal virialization can drive an efficien...

We study the evolution of spectral early-type galaxies in clusters, groups, and the field up to redshift 0.9 using the ESO Distant Cluster Survey (EDisCS) dataset. We measure structural parameters (circularized half-luminosity radii Re, surface brightness Ie, and velocity dispersions σ) for 154 cluster and 68 field galaxies. On average, we achieve precisions of 10% in Re, 0.1 dex in log Ie, and...

We present HST NIC2 morphologies of a spectroscopic sample of massive galaxies at z ∼ 2.3, by extending our sample of nine compact quiescent galaxies (re ∼ 0.9 kpc) with ten massive emissionline galaxies. The emission-line galaxies are classified by the nature of their ionized emission; there are six star-forming galaxies and four galaxies hosting an active galactic nucleus (AGN). The starformi...

We present HST NIC2 morphologies of a spectroscopic sample of massive galaxies at z ∼ 2.3, by extending our sample of nine compact quiescent galaxies (re ∼ 0.9 kpc) with ten massive emissionline galaxies. The emission-line galaxies are classified by the nature of their ionized emission; there are six star-forming galaxies and four galaxies hosting an active galactic nucleus (AGN). The starformi...

We present an analysis of the structures, sizes, star formation rates, and local environmental properties of galaxies at z ∼ 4 − 6 (τuniverse < 2 Gyr), utilising deep Hubble Space Telescope imaging of the Hubble Ultra Deep Field. The galaxies we study are selected with the Lyman-break drop-out technique, using galaxies which are B-,V-, and i−drops, which effectively selects UV bright starbursti...

We present an analysis of the structures, sizes, star formation rates and local environmental properties of galaxies at z ∼ 4–6 (τ universe < 2 Gyr), utilizing deep Hubble Space Telescope imaging of the Hubble Ultra Deep Field. The galaxies we study are selected with the Lymanbreak drop-out technique, using galaxies which are B-, Vand i-drops, which effectively selects ultraviolet (UV) bright s...

We have measured the angular correlation function, w(θ), of radio sources in the 1.4 GHz NVSS and FIRST radio surveys. Below ∼ 6′ the signal is dominated by the size distribution of classical double radio galaxies, an effect underestimated in previous studies. We model the physical size distribution of FRII radio galaxies to account for this excess signal in w(θ). The amplitude of the true cosm...