Oral Abstract

Oral Contribution (O0.3) Joeri van Leeuwen (University of Amsterdam)

First Results and Data from the Apertif Surveys

Apertif is the new phased-array feed that increases the Westerbork Synthesis Radio Telescope field ofview by a factor 30. It turns this interferometer into a natural survey instrument, one of the most sensitivein the world. On 1 July 2019, the Apertif legacy surveys commenced and we present the first resultshere. These are a time-domain survey and a two-tiered imaging survey. In time domain, we find FastRadio Bursts (FRBs). As Apertif uniquely combines a large field of view with relatively long baselines,and a powerful dedicated supercomputer, the survey provides both very good detection rates and solidlocalisation. Those are essential for determining the nature of these enigmatic bursts. The imagingsurvey has shallow and medium-deep components, to provide neutral hydrogen (HI), radio continuumand polarization data products across a bandwidth of 300 MHz, corresponding to a redshift of 0.26 forHI. Its key science goals are studying the role of environment and interaction on galaxy properties andgas removal, finding the smallest galaxies, connecting cold gas to AGN, understanding the faint radiopopulation, and studying magnetic fields in galaxies. We will highlight the first results. We detected andlocalised multiple FRBs, probing the magneto-ionic medium along their lines of sight. We discovered andmonitored an intra-hour variable. We determined resolved spectral indices from combining with LOFARdata. Survey data and products are served to the community via the Apertif Long Term Archive (ALTA).Available data products include time-domain real-time alerts, and filterbank data; and imaging rawvisibilities, calibration tables, calibrated visibilities, multi-frequency synthesis continuum images,polarization images and cubes, and uncleaned neutral hydrogen (HI) line and beam cubes.