A method for determining radio continuum spectra and its application to large surveys

¹ CDS, Observatoire astronomique de Strasbourg, UMR 7550, 11 rue de l'Université, 67000 Strasbourg, France e-mail: bvollmer@astro.u-strasbg.fr
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn Germany
³ UMR 5572, Observatoire Midi-Pyrénées, 14 avenue E. Belin, 31400 Toulouse, France
⁴ Observatoire de Paris, Section de Meudon, GEPI, CNRS UMR 8111 and Université Paris 7, 5 place Jules Janssen, 92195 Meudon Cedex, France

Received: 30 March 2004
Accepted: 19 October 2004

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 independent radio cross-identifications and ∼ 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.