Community Research and Development Information Service - CORDIS


LOFARCORE Report Summary

Project ID: 339743
Funded under: FP7-IDEAS-ERC
Country: Netherlands

Mid-Term Report Summary - LOFARCORE (Unravelling the Cosmic Reionization History)

An important phase in the history of the Universe was the transition from a mostly neutral (hydrogen) state to an almost fully ionized state (protons and electrons). This change came about, so we think, as a result of the appearance of the first luminous stars and black holes which formed in small galaxies. These objects are powerful sources of UV and X-ray radiation which ionise and heat the cold and still pristine medium permeating the Universe in that early phase. This period is called the Epoch of Reionization and probably took place between 300 and 800 million years after the Big Bang; i.e. when the Universe was in its childhood years. The Universe was obviously much smaller then and the radiation emitted during this phase has since been 'redshifted' by the almost tenfold expansion of the Universe. This shifted 21cm line emission of neutral hydrogen, which is emitted at the (rest)frequency of 1420 MHz, to a frequency of approximately 120-170 MHz. These frequencies are a good match to the LOFAR telescope, which is situated in the Northern part of the Netherlands but with outliers all over Europe. However, it will take several thousand hours of night-time observing to detect the extremely faint signals. We have now accumulated more than 10 PetaByte of raw data in the past 3 years and will continue to observe in the future. We have entered the realm of Big Data.

The processing of all this data - on a dedicated powerful computer with 1536 CPU cores, and 128 GPUs located at the University of Groningen - has been ongoing for more than 2 years and we have slowly but steadily learned how to do this. In the process, we have made the deepest radio continuum images, as well as the highest resolution images, ever made at low frequencies. We have also learned that the synchrotron emission from our Galaxy is very highly polarized. We have also collected exquisite information on the fine-scale structure and the dynamics of the ionosphere, the thick plasma layer located between 200 and 700 km above the Earth surface. The ionospheric plasma can be very turbulent (especially at night) leading to 'scintillation', a phenomenon well-known in the optical. The data are not astronomically useful under such conditions, which occur about 20% of the time. Collecting data on all of the above was crucial to calibrate our data to a precision that has never before been achieved. We are now at the point that we can start to steer the data through our processing pipeline. In the next few years we expect to produce a steady stream of results, ultimately leading to a detection of the signals. These should answer the most intriguing questions: "When did the reionization of the Universe begin?", "How long did this process take?" and "What objects are responsible?".

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