Multi-frequency measurements of the NVSS foreground sources in the cosmic background imager fields I. Data release

Context. We present the results of the flux density measurements at 4.85 GHz and 10.45 GHz of a sample of 5998 NVSS radio sources with the Effelsberg 100 m telescope. Aims. The initial motivation was the need to identify the NVSS radio sources that could potentially contribute significant contaminating flux in the frequency range at which the Cosmic Background Imager experiment operated. Methods. An efficient way to achieve this challenging goal has been to compute the high frequency flux density of those sources by extrapolating their radio spectrum. This is determined by the three-point spectral index measured on the basis of the NVSS entry at 1.4 GHz and the measurements at 4.85 GHz and 10.45 GHz carried out with the 100 m Effelsberg telescope. Results. These measurements are important since the targeted sample probes the weak part of the flux density distribution, hence the decision to make the data available. Conclusions. We present the table with flux density measurements of 3434 sources that showed no confusion allowing reliable measurements, their detection rates, their spectral index distribution and an interpretation which explains satisfactorily the observed uncertainties.