First image with Apertif: a new life for the Westerbork radio telescope

© Astron

An important milestone for the Westerbork Synthesis Radio Telescope: the first images have been made using a revolutionary new type of receiver, called Apertif. Because of these new receivers, much larger areas of sky can be mapped in a single observation. The 'old' Westerbork telescope could only map an area of sky comparable in size to that of the full moon in a single observation. The new Westerbork/Apertif system can image a region of sky 40 times larger, which is a great step forward. The new Apertif receivers, developed by ASTRON in Dwingeloo, were installed on the Westerbork telescope over the last year and will be fully operational this autumn.

With the upgraded Westerbork telescope there are numerous possibilities for new studies. In particular, Apertif will be used to make radio images of large areas of sky that have not been studied before and to search the sky for new and interesting types of objects. In addition, with Apertif this can be done with an amount of detail that was not possible before. This unique capability will be used to image large parts of the northern sky and provide a public database of images and catalogues that will be used for many astronomical projects done by astronomers from all over the world.

The first images made with the upgraded telescope that demonstrate this new 'wide-angle' capability is shown here. The first image shows the dwarf galaxy Leo T. The image is colour-coded and shows the gas (in blue) in this galaxy together with many distant radio galaxies in the background shown in orange. For comparison, the field of view of the previous Westerbork system and the size of the full moon are also indicated.

To make this new capability possible, ASTRON developed and built the hardware in-house. 121 small receivers are used in each telescope whose signals are combined electronically to produce the large field of view.

The upgraded telescope will also be used to search for and study new variable sources in the radio sky. With the new Apertif receivers, observations of large parts of the sky can be done much faster, and projects that used to be impossible as they would take tens of years can now be done in a much shorter time. Westerbork is therefore poised to make many new discoveries in the radio sky.