NIKA2 unveils and pinpoints the Planck compact sources

Context. The Planck Catalogue of Compact Sources (PCCS2) is an unbiased census of the millimetre sky at sub-Jansky levels, and thus a valuable resource for studies of galaxy evolution. Nevertheless, its application to extra-galactic studies is hindered by its limited angular resolution of a few arcminutes. Aims. In order to open the PCCS2 for an in-depth exploitation, understanding whether they are active galactic nuclei, dusty star forming galaxies, proto-clusters, or chance alignments is paramount. Improving the positional information and angular resolution will also be beneficial in this quest. Here we aim to unveil the PCCS2 sources in the northern hemisphere. Methods. We observed the bright end of the 143 and 217 GHz PCCS2 at Dec >= -41.2 degrees with the New IRAM KID Arrays 2 camera (NIKA2) at 1.2 mm (260 GHz) and 2.0 mm (150 GHz). The sample includes 487 targets. Map making and source extraction were carried out with the latest version of the NIKA2 data reduction software. Results. NIKA2 detected 54% and 77% of the targets at 1.2 and 2.0 mm. More than 95% are point-like sources, five are resolved in two components, and only 4% are extended at the resolution of NIKA2. By cross-matching the NIKA2 catalogue to the NASA Extragalactic Database, the redshift of similar to 86% of the sources was found, covering the range from z similar to 0 to 3.4, with a median z = 0.77. Conclusions. The number density of the 143 GHz PCCS2 is 0.029 deg(-2), in good agreement with model predictions. Roughly 80% of these sources are QSOs or AGN, with a median NIKA2 spectral index alpha = -1.15, typical of non-thermal synchrotron emission. With a positional accuracy smaller than 3.0 arcsec, and an angular resolution of 11.6 and 18.0 arcsec at 1.2 and 2.0 mm, respectively, the NIKA2 PCCS2 catalogue is hereby released to the community.