The core fundamental plane of B2 radio galaxies

The photometric, structural and kinematical properties of the centers of elliptical galaxies, harbor important information of the formation history of the galaxies. In the case of non active elliptical galaxies these properties are linked in a way that surface brightness, break radius and velocity dispersion of the core lie on a fundamental plane similar to that found for their global properties. We construct the Core Fundamental Plane (CFP) for a sizeable sample of low redshift radio galaxies and compare it with that of non radio ellipticals. To pursue this aim we combine data obtained from high resolution HST images with medium resolution optical spectroscopy to derive the photometric and kinematic properties of ~40 low redshift radio galaxies. We find that the CFPs of radio galaxies is indistinguishable from that defined by non radio elliptical galaxies of similar luminosity. The characteristics of the CFP of radio galaxies are also consistent (same slope) with those of the Fundamental Plane (FP) derived from the global properties of radio (and non radio) elliptical galaxies. The similarity of CFP and FP for radio and non radio ellipticals suggests that the active phase of these galaxies has minimal effects for the structure of the galaxies.Comment: 8 pages, 4 figures, accepted for publication in Astronomy and Astrophysic

The ATESP 5 GHz radio survey. II. Physical properties of the faint radio population

One of the most debated issues about sub-mJy radio sources, which are responsible for the steepening of the 1.4 GHz source counts, is the origin of their radio emission. Particularly interesting is the possibility of combining radio spectral index information with other observational properties to assess whether the sources are triggered by star formation or nuclear activity. The aim of this work is to study the optical and near infrared properties of a complete sample of 131 radio sources with S>0.4 mJy, observed at both 1.4 and 5 GHz as part of the ATESP radio survey. We use deep multi-colour (UBVRIJK) images, mostly taken in the framework of the ESO Deep Public Survey, to optically identify and derive photometric redshifts for the ATESP radio sources. Deep optical coverage and extensive colour information are available for 3/4 of the region covered by the radio sample. Typical depths of the images are U~25, B~26, V~25.4, R~25.5, I~24.3, 19.5<K_s<20.2, J<22.2. Optical/near infrared counterparts are found for ~78% (66/85) of the radio sources in the region covered by the deep multi-colour imaging, and for 56 of these reliable estimates of the redshift and type are derived. We find that many of the sources with flat radio spectra are characterised by high radio-to-optical ratios (R>1000), typical of classical powerful radio galaxies and quasars. Flat-spectrum sources with low R values are preferentially identified with early type galaxies, where the radio emission is most probably triggered by low-luminosity active galactic nuclei. Considering both early type galaxies and quasars as sources with an active nucleus, such sources largely dominate our sample (78%). Flat-spectrum sources associated with early type galaxies are quite compact (d<10-30 kpc), suggesting core-dominated radio emission.Comment: 15 pages, 13 figures, accepted for pubblication in A&

The ATESP Radio Survey II. The Source Catalogue

This paper is part of a series reporting the results of the Australia Telescope ESO Slice Project (ATESP) radio survey obtained at 1400 MHz with the Australia Telescope Compact Array (ATCA) over the region covered by the ESO Slice Project (ESP) galaxy redshift survey. The survey consists of 16 radio mosaics with ~8"x14" resolution and uniform sensitivity (1sigma noise level ~79 microJy) over the whole area of the ESP redshift survey (~26 sq. degrees at decl. -40 degr). Here we present the catalogue derived from the ATESP survey. We detected 2960 distinct radio sources down to a flux density limit of ~0.5 mJy (6sigma), 1402 being sub-mJy sources. We describe in detail the procedure followed for the source extraction and parameterization. The internal accuracy of the source parameters was tested with Monte Carlo simulations and possible systematic effects (e.g. bandwidth smearing) have been quantified.Comment: 14 pages, 14 Postscript figures, Accepted for publication in A&A Suppl. Corrected typos and added Journal Referenc