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Initiator: ASTRON Netherlands Institute for Radio Astronomy

eu  SNN

This project was co-financed by the EU, the European Fund for Regional Development and the Northern Netherlands Provinces (SNN), and EZ/KOMPAS.

High resolution LOFAR image of 3C61.1

Copyright: Reinout van Weeren (University of Leiden)/ASTRON

In december 2009 a long observing run was carried out on the extragalactic radio source 3C61.1. For this 60 hour observation a total of 20 LOFAR HBA stations were used, consisting of 16 split core stations and 4 remote stations.

The processing of the data started with automatic removal of radio frequency interference. The initial model for the calibration consisted of two point sources, representing the two hotspots of the radio source. The hotspots are the two bright objects visible in the right panel of the image. The model was subsequently refined using the technique of selfcalibration. The final image has an impressive resolution of 9.7 by 9.4 arcsec by making use of uniform weighting (which optimizes the resolution of the image). The HBA image was made using only one subband at 173 MHz. This is only a small fraction of the available data for the 60 hour observation. A next step will be to combine all available subbands to create an even better image.

For comparison, images of 3C61.1 from other radio telescopes are shown. The VLSS 74 MHz image was made with the Very Large Array (VLA), New Mexico (USA). The VLA 1.5 GHz image is from Leahy & Perley (1991, AJ, 102, 537). The WENSS survey was carried out with the Westerbork Synthesis Radio Telescope located not far away from the central core of LOFAR.

ASTRON initiated LOFAR as a new and innovative effort to force a breakthrough in sensitivity for astronomical observations at radio-frequencies below 250 MHz. 
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