H. R. de Ruiter

The VLA-VIRMOS Deep Field I. Radio observations probing the microJy source population

We have conducted a deep survey (r.m.s noise 17 microJy) with the Very Large Array (VLA) at 1.4 GHz, with a resolution of 6 arcsec, of a 1 square degree region included in the VIRMOS VLT Deep Survey. In the same field we already have multiband photometry down to I(AB)=25, and spectroscopic observations will be obtained during the VIRMOS VLT survey. The homogeneous sensitivity over the whole field has allowed to derive a complete sample of 1054 radio sources (5 sigma limit). We give a detailed description of the data reduction and of the analysis of the radio observations, with particular care to the effects of clean bias and bandwidth smearing, and of the methods used to obtain the catalogue of radio sources. To estimate the effect of the resolution bias on our observations we have modelled the effective angular-size distribution of the sources in our sample and we have used this distribution to simulate a sample of radio sources. Finally we present the radio count distribution down to 0.08 mJy derived from the catalogue. Our counts are in good agreement with the best fit derived from earlier surveys, and are about 50 % higher than the counts in the HDF. The radio count distribution clearly shows, with extremely good statistics, the change in the slope for the sub-mJy radio sources.

In search of dying radio sources in the local universe

Aims. Up till now very few dying sources were known, presumably because the dying phase is short at centimeter wavelengths. We therefore have tried to improve the statistics on sources that have ceased to be active, or are intermittently active. The latter sources would partly consist of a fossil radio plasma left over from an earlier phase of activity, plus a recently restarted core and radio jets. Improving the statistics of dying sources will give us a better handle on the evolution of radio sources, in particular the frequency and time scales of radio activity. Methods. We have used the WENSS and NVSS surveys, in order to find sources with steep spectral indices, associated with nearby elliptical galaxies. In the cross correlation we presently used only unresolved sources, with flux densities at 1.4 GHz larger than 10 mJy. The eleven candidates thus obtained were observed with the VLA in various configurations, in order to confirm the steepness of the spectra, and to check whether active structures like flat-spectrum cores and jets are present, perhaps at low levels. We estimated the duration of the active and relic phases by modelling the integrated radio spectra using the standard models of spectral evolution. Results. We have found six dying sources and three restarted sources, while the remaining two candidates remain unresolved also with the new VLA data and may be Compact Steep Spectrum sources, with an unusually steep spectrum. The typical age of the active phase, as derived by spectral fits, is in the range 10 7 −10 8 years. For our sample of dying sources, the age of the relic phase is on average shorter by an order of magnitude than the active phase.

The ATESP radio survey - III. Source counts

This paper is part of a series reporting the results of the ATESP radio survey obtained at 1.4 GHz with the Australia Telescope Compact Array. The survey consists of 16 radio mosaics with ∼

The HST survey of the B2 sample of radio-galaxies: Optical nuclei and the FR I/BL Lac unified scheme

8\arcsec \times 14\arcsec

The VVDS-VLA Deep Field II. Optical and near infrared identifications of VLA S(1.4GHz)>80 microJy sources in the VIMOS VLT Deep Survey VVDS-02h field

resolution and uniform sensitivity (

The ATESP radio survey - IV. Optical identifications and spectroscopy in the EIS-A region

1 \sigma

A multi-frequency study of the radio galaxy NGC 326 - I. The data

noise level ∼ 79 μ Jy) over the whole area of the ESO Slice Project redshift survey ( ∼ 26 sq. degr. at

HST images of B2 radio galaxies: A link between circum-nuclear dust and radio properties?

\delta \sim -40\degr

Is cold gas fuelling the radio galaxy NGC 315

). The ATESP survey has produced a catalogue of 2960 radio sources down to a flux limit (

The HST survey of the B2 sample of radio galaxies: Detection of two optical jets

6\sigma