The surveys planned for Apertif are the result of discussions within the Apertif Science Team, in consultation with the international astronomical community. Many of the scientists planning to use SKA1 and its pathfinders have been involved in developing the Apertif Survey Plan. Therefore, the science planned for Apertif is an integral part of the science planned for SKA1 and its pathfinders. A second, important consideration for defining the Apertif surveys has been the legacy value of the Apertif data.

The Apertif surveys will consist of:

• a large-area, shallow imaging survey of HI and polarised radio continuum emission covering ~3500 deg²;
• a medium-deep imaging survey of HI and polarised radio continuum emission covering ~ 450 deg²;
• a time-domain survey for pulsars and fast transients over 15,000 deg²;
• in addition to these large surveys, a small amount of observing time will be devoted to imaging a number of small survey regions (typically 10 deg² in size) coincident with fields from the Tier 2 of the LOFAR imaging continuum survey.

The main science topics addressed by the Apertif Surveys are:

• use resolved HI observations to investigate the connections of the gas- and total mass distribution of galaxies over a wide range of galaxy properties as obtained from other wavebands
• investigate how these relations vary with environment and what role interactions, gas accretion and removal of gas play;
• investigate the properties of the smallest gas-rich galaxies in the local Universe and confront these with theory;
• study the role of cold gas in AGN and their feedback activity;
• study the history of star formation and AGN activity of the faint radio continuum population;
• study the magnetic fields in galaxies and of the large-scale structures in which they are embedded;
• the detection, characterisation and arcsec-localisation of fast radio bursts (FRBs) over the Northern sky;
• perform a census of intermittent and normal pulsars along the Galactic Plane;
• study the (orphan) afterglows of Gamma Ray Bursts and Tidal Disruption Events.

A full description of the Apertif surveys can be found in the Apertif Survey Plan document.

Layout of the Apertif Surveys.The red dots indicate pointings of the Medium-Deep Survey, while the small black dots indicate those of the Shallow Survey. The black squares give the locations of the special LOFAR fields that will also be imaged by Apertif.

The red, dashed line indicates δ = 30 ̊. The blue rectangle shows the location of the Herschel-Atlas field, while the green box indicated the rough outline of the HetDex survey area. The grey, curly contour indicates the locations where the Galactic foreground extinction is 1 magnitude in the V band