GALACTICNUCLEUS: A high-angular-resolution JHKs imaging survey of the Galactic centre II. First data release of the catalogue and the most detailed CMDs of the GC

The high extinction and extreme source crowding of the central regions of the Milky Way are serious obstacles to the study of the structure and stellar population of the Galactic centre (GC). Existing surveys that cover the GC region (2MASS, UKIDSS, VVV, SIRIUS) do not have the necessary high angular resolution. Therefore, a high-angular-resolution survey in the near infrared is crucial to improve the state of the art. Here, we present the GALACTICNUCLEUS catalogue, a near infrared $JHK_s$ high-angular-resolution ($0.2''$) survey of the nuclear bulge of the Milky Way. We explain in detail the data reduction, data analysis, calibration, and uncertainty estimation of the GALACTICNUCLEUS survey. We assess the data quality comparing our results with previous surveys. We obtained accurate $JHK_s$ photometry for $\sim 3.3\times10^6$ stars in the GC detecting around 20 \% in $J$, 65 \% in $H,$ and 90 \% in $K_s$. The survey covers a total area of $\sim0.3$ square degrees, which corresponds to $\sim 6,000$ pc$^2$. The GALACTICNUCLEUS survey reaches 5\,$\sigma$ detections for $J \sim 22$ mag, $H \sim 21$ mag, and $K_s \sim 21$ mag. The uncertainties are below 0.05 mag at $J \sim 21$ mag, $H \sim 19$ mag, and $K_s \sim 18$ mag. The zero point systematic uncertainty is $\lesssim0.04$ mag in all three bands. We present colour-magnitude diagrams for the different regions covered by the survey.