Astronomy Colloquium

The LOFAR EoR project set out to measure the spatial power spectrum (PS) of redshifted HI signals in the redshift range from z = 6 to 11.4. WMAP and Planck data suggest that this redshift range will cover the most interesting phases of the Epoch of Reionization, a key phase in the history of the Universe. Among the main questions we are after are the redshift evolution of the spatial PS and what it might tell us about the sources of reionization.

The data taking, in two windows centered on the NCP and the source 3C196, started in earnest in Dec 2012 and will soon embark on its fourth (Winter) observing season. Thusfar we have accumulated about 1500 h of data. The project faces a wide variety of challenges. Many of these had been expected and are well understood.  Among these are RFI, ionospheric effects, calibrating and processing a Petabyte of data, and dealing with (polarized) Galactic foregrounds.

Constructing an accurate high resolution sky model and solving for direction-dependent complex gains (due to time-varying station beams and ionospheric turbulence) have proved more difficult and time consuming.  I will describe and illustrate these challenges and how we are trying to solve them. In the mean time we are collecting interesting results on ancillary science related to Galactic and extragalactic foregrounds, especially as regards to their polarization. I will conclude with the project status and timeline.