First release of Apertif imaging survey data

Context. Apertif is a phased-array feed system for the Westerbork Synthesis Radio Telescope, providing forty instantaneous beams over 300 MHz of bandwidth. A dedicated survey program utilizing this upgrade started on 1 July 2019, with last observations taken 28 February 2022. The imaging component provides radio continuum, polarization, and spectral line data. Aims. Public release data critical maximizing legacy survey. Toward that end, we describe products from first year operations, through 30 June 2020. In particular, focus defining quality control metrics processed products. Methods. pipeline, Apercal, automatically produces non-primary beam corrected continuum images, polarization images cubes, uncleaned dirty cubes each an observation. For release, are considered beam-by-beam basis within We validate by using identify deviations Gaussian noise in residual images. If image passes validation, all given beam. apply further validation to provide flags indicating those Results. raw observational observations, total 221 160 independent target fields, covering approximately one thousand square degrees sky. Images released per basis, 3374 (of 7640 considered) released. median 41.4 uJy ?1 , slightly lower 36.9 Stokes V image. angular resolution 11.6?/sin ? . 36.6 kHz, 1.6 mJy corresponding 3- ? H i column density sensitivity 1.8 × 10 20 atoms cm ?2 km s (for 24? 15?). Line at frequency have higher values, consistent global RFI environment overall performance. also primary individual compound made accessible Virtual Observatory interface can be queried variety standard tools.