Commissioning LOFAR for polarisation observations

• Applicants: Dr. Rainer Beck; Professor Dr. Ulrich Klein
• Subject Area: Astrophysics and Astronomy
• Term: from 2010 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 108727618

Measuring linearly polarised radio emission at low frequencies and with a software telescope such as LOFAR opens exciting scientific prospects, but is technically challenging. The construction of non-moving telescope elements results in high instrumental polarization which varies with position on the sky and with distance from the beam center and needs appreciable correction efforts. Furthermore, Faraday rotation in the Earth's ionosphere is different for each direction and for each LOFAR station. The imaging software needs to account for all of these effects. Until now the distorting effects could be identified and analysed in this project. New calibration procedures were developed, leading to radio maps in total intensity. Polarised emission from several pulsars and from a region in the Milky Way was successfully detected.These commissioning efforts are to be continued and finalised over the next years. These efforts shall be conducted by the postdoc at the MPIfR, who should continue to lead these efforts and supervise the students from the other projects in technical issues. He should be supported by a new PhD student at AlfA who should develop calibration methods for polarisation, including corrections for instrumental polarisation and ionospheric Faraday Rotation.

• DFG Programme: Research Units
• Subproject of: FOR 1254: Magnetisation of Interstellar and Intergalactic Media: The Prospects of Low-Frequency Radio Observations
• Participating Person: Dr. James M. Anderson