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

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 similar to 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.