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radioforegrounds Report Summary

Project ID: 307209
Funded under: FP7-IDEAS-ERC
Country: United Kingdom

Final Report Summary - RADIOFOREGROUNDS (Enabling cosmology with radio astronomy surveys: dealing with foreground contamination)

The ERC project “Enabling cosmology with radio astronomy surveys: dealing with foreground contamination” tackles the problem of foreground contamination for cosmology surveys. Two key areas of cosmology are measurements of the cosmic microwave background (CMB) from the early Universe and intensity mapping that will map the large-scale structure of the Universe. Measurements of the B-mode polarization of the CMB is a key test of inflation and allows further refinement in the current cosmological model. Intensity mapping (IM) is a new technique that aims to map large cosmological volumes of the Universe in an emission line (such as the 21cm HI line from atomic hydrogen) as a function of redshift i.e. in 3-D. Large IM surveys are currently being planned and could potentially revolutionise cosmology. The data will be complementary to other large scale galaxy surveys being undertaken at optical wavelengths (e.g. EUCLID), where systematic errors are likely to dominate. Both topics are key to understanding key problems in cosmology such as did inflation occur shortly after the Big Bang, and what is the nature of dark energy. However, both measurements suffer from contamination by foregrounds such as synchrotron emission from our Galaxy.

We have improved the understanding of microwave foregrounds for CMB data, by developing state-of-the-art component separation algorithms that use both frequency and spatial information. One algorithm, the Generalized Needlet ILC, has been successfully applied to Planck data to produce several official Planck products including CMB maps, SZ maps, as well as CIB-free thermal dust maps. The GNILC algorithm has also been extended to the field of IM, where it has been shown to perform well for both HI IM and CO IM.

We have studied specific components of foreground emissions, such as synchrotron emission and the mysterious Anomalous Microwave Emission (AME). Using Planck data, in combination with multi-frequency ancillary data, we have constrained the spectrum of synchrotron emission. The standard synchrotron template of Haslam et al. has been improved by destriping and source removal. We have also identified AME to be likely due to electric dipole emission from small spinning dust grains. Numerous new AME regions have been identified for further study. Our measurements show that AME is an important foreground in intensity but is probably sub-dominant in polarization.

We have developed a new IM concept - BINGO - that uses a drift-scanning total-power single dish telescope. Through our work, we have managed to find funding via Brazil’s FAPESP funding agency. The experimental design and concept is now advanced and construction will begin soon. This is one of a small number of funded HI IM experiments currently moving forward, which will be vital as pathfinders for the ultimate radio telescope - the Square Kilometre Array (SKA).

We have developed an end-to-end simulation pipeline for IM experiments. This allows detailed testing of data and systematics such as scan strategies, noise properties, systematics, map-making etc. We have used simulations to forecasts the performance of IM surveys from BINGO, SKA etc. We have used it to consider consider certain types of systematics such as standing waves and 1/f in the receiver. We have also used it to produce detailed simulations of the effect of radio frequency interference (RFI) from navigation satellites that will ultimately limit the sensitivity of future surveys.

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United Kingdom
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