Abstract.Simbad is the reference database for identification and bibliography of astronomical objects. It contains identifications, "basic data", bibliography, and selected observational measurements for several million astronomical objects.Simbad is developed and maintained by CDS, Strasbourg. Building the database contents is achieved with the help of several contributing institutes. Scanning the bibliography is the result of the collaboration of CDS with bibliographers in Observatoire de Paris (DASGAL), Institut d'Astrophysique de Paris, and Observatoire de Bordeaux.When selecting catalogues and tables for inclusion, priority is given to optimal multi-wavelength coverage of the database, and to support of research developments linked to large projects. In parallel, the systematic scanning of the bibliography reflects the diversity and general trends of astronomical research.A WWW interface to Simbad is available at: http://simbad.u-strasbg.fr/Simbad.

Abstract. We present the new catalog of principal galaxies (PGC2003). It constitutes the framework of the HYPERLEDA database that supersedes the LEDA one, with more data and more capabilities. The catalog is still restricted to confirmed galaxies, i.e. about one million galaxies, brighter than ≈18 B-mag. In order to provide the best possible identification for each galaxy we give: accurate coordinates (typical accuracy better than 2 arcsec), diameter, axis ratio and position angle. Diameters and axis ratios have been homogenized to the RC2 system at the limiting surface brightness of 25B − mag arcsec −2 , using a new method, the EPIDEMIC method. In order to provide the best designation for each galaxy, we collected the names from 50 catalogues. The compatibility of the spelling is tested against NED and SIMBAD, and, as far as possible we used a spelling compatible with both. For some cases, where no consensus exists between NED, SIMBAD and LEDA, we propose some changes that could make the spelling of names fully compatible. The full catalog is distributed through the CDS and can be extracted from HYPERLEDA.

The new release of the SPECFIND radio cross-identification catalogue, SPECFIND V2.0, is presented. It contains 107488 crossidentified objects with at least three radio sources observed at three independent frequencies. Compared to the previous release the number of entry radio catalogues is increased from 20 to 97 with 115 tables. This large increase was only made possible by the development of four tools at the Centre de Données astronomiques de Strasbourg (CDS) which use the standards and infrastructure of the Virtual Observatory (VO). This was done in the framework of the VO-TECH European Design Study of the Sixth Framework Program. We give an overview of the different classes of radio sources that a user can encounter. Due to the increase of the frequency coverage of the input radio catalogues, this release demonstrates that the SPECFIND algorithm is able to detect spectral breaks around a frequency of ∼1 GHz.

Abstract.A new tool to extract cross-identifications and radio continuum spectra from radio catalogues contained in the VIZIER database of the CDS is presented. The code can handle radio surveys at different frequencies with different resolutions. It has been applied to 22 survey catalogues at 11 different frequencies containing a total of 3.5 million sources, which resulted in over 700 000 independent radio cross-identifications and ∼67 000 independent radio spectra with more than two frequency points. A validation of the code has been performed using independent radio cross-correlations from the literature. The mean error of the determined spectral index is ±0.3. The code produces an output of variable format that can easily be adapted to the purpose of the user.

Abstract. The accuracy in position and flux density of 19 large radio continuum source catalogues has been determined using SPECFIND, a new tool recently made available through the CDS. The ∼67 000 radio continuum spectra with three or more frequencies produced by SPECFIND were used to cross-correlate sources from different catalogues and to calculate offsets in right ascension and declination in the various catalogues with respect to the positions given in the NRAO VLA Sky Survey (NVSS) catalogue, which was adopted as a reference. The flux densities reported in the catalogues were compared to those predicted by the composite spectra, enabling us to assess the quality of the flux density calibration of the different catalogues.