LOFAR – a new low-frequency radio telescope

Abstract

LOFAR, the Low Frequency Array, is a new low frequency telescope that is currently being built in the Netherlands. It will initially observe at frequencies from 30 to 240 MHz with baselines of up to 100 km. The aim for the second phase is to carry out sensitive observations below 30 MHz and to extend the maximum baselines up to 400 km. The design of LOFAR is driven by four fundamental astrophysical applications: (i) the epoch of reionisation; (ii) extragalactic surveys and their exploitation to study the formation and evolution of clusters, galaxies, and black holes; (iii) transient sources and their association with high energy objects such as gamma ray bursts; and (iv) cosmic ray showers and their exploitation to study the origin of ultra-high energy cosmic rays. Particularly relevant for this conference is LOFAR's ability to study the epoch of reionisation through observations of the redshifted 21 cm line. This will address several important issues including the source of reionisation and the reionisation history of the Universe. In addition to the science case, LOFAR's instrumental concepts and time line are briefly reviewed. The main technical challenges for LOFAR include rejection of man-made radio interference, dealing with the corrupting influence of the ionosphere on the observations, and minimising contaminations of the EOR signal by foreground discrete astrophysical sources.