The SPECFIND V3.0 catalog of radio continuum cross-identifications and spectra: Reaching lower frequencies

Context. Many radio continuum catalogs with different sensitivity limits and spatial resolutions are published via the VizieR database at the Centre de Données astronomiques de Strasbourg. The diversity of spatial resolutions of different catalogs makes the cross-identification of different flux density measurements of individual sources complex. The SPECFIND tool is able to handle radio surveys at different frequencies from different instruments with different resolutions. Aims. Since the former version of the SPECFIND catalog was released ten years ago, hundreds of new radio continuum catalogs have been published. We upgraded the SPECFIND tool to reach a wider frequency range, especially the lower-frequency radio regime, as well as to have better spatial sky coverage. Methods. We adapted selection criteria and applied them to all of the radio catalogs listed in the VizieR database to define a final sample of new catalogs. We unified the new catalogs and implemented them in the SPECFIND tool. The new SPECFIND V3.0 radio cross-identification catalog was constructed using 204 input tables from 160 VizieR radio continuum catalogs to cross-identify flux density measurements of individual sources and fit their spectral slopes. We discuss the frequency and sky coverage of all processed catalogs and compare the results to the previous version. Furthermore, we present and investigate peaked spectrum (PS) sources with spectral breaks around 1.4 GHz and 325 MHz. Results. By increasing the number of input catalog tables that were implemented in SPECFIND from 115 to 204 (89 new catalog tables and two updates), we improved the number of resulting spectra from ∼107 500 to ∼340 000 and increased the number of cross-identified sources from ∼600 000 to ∼1.6 million. The final SPECFIND V3.0 catalog is publicly available via VizieR. By applying SPECFIND to two subsamples of the catalogs with frequency cuts at 325 MHz and 1.4 GHz, spectral break and PS source candidates could be identified. We encourage follow-up observations of these candidates to confirm their nature because the population we identify has a relatively low reliability. Conclusions. The SPECFIND V3.0 catalog is a very useful resource and a powerful open access tool, reachable via VizieR. By tripling the resulting spectra and including many radio continuum surveys from the last 50 years, we provide a significantly extended catalog of cross-identified radio continuum sources. Furthermore, the SIMBAD database will be updated using the SPECFIND V3.0 catalog and will contain more radio continuum data, serving the needs of future projects.