Euclid Science Preparation

Lead Research Organisation: University of Portsmouth
Department Name: Institute of Cosmology and Gravitation


This grant is to support the Euclid satellite, a selected M-class mission in European Space Agency Cosmic Vision programme. Euclid is due to be launched in 2020, and is designed to tackle some of the biggest questions in cosmology and astrophysics. This field is experiencing a golden age of discovery driven by new experiments and theoretical advances. However, we still face three fundamental challenges before a more complete model of the Universe can be achieved: i) What are the properties of the "dark matter" and "dark energy" that make up 96% of the Universe? ii) How do galaxies form and evolve? iii) What is the origin and distribution of structures in the Universe?

Euclid will address these fundamental problems by performing an enormous galaxy survey, measuring the angular positions of 150 million galaxies, and taking spectra for 45 million of them. This survey will allow multiple physical processes to be measured and their corresponding parameters determined. While the design of the survey aims to measure the accelerated expansion of the Universe, these data have tremendous legacy value, with optical imaging at spatial resolution similar to Hubble over a third of the night sky, imaging 1.5 billion galaxies for weak lensing shape measurement, infrared imaging in 3 bands with only slightly worse spatial resolution, and spectra and redshifts of 40 million galaxies. This dataset can only be obtained from space, and will be used by scientists worldwide in a wide range of contexts, and it will have huge public outreach potential.

Euclid will also be capable of undertaking additional science surveys during the nominal mission, enabling ground-breaking research in the areas of cool exoplanets, and supernovae & transients. Working groups set up to study these possibilities both have UK leadership.

UK work on the payload instruments and the Euclid Ground Segment are supported by UKSA grants. The output from these systems is data products up to the level of measurement statistics (known as power spectra and correlations functions). These data will require extremely careful analysis and comparison to accurate theoretical models. The preparatory work needs to start now, given the range and level of accuracy required. This grant application requests support for this work, particularly focussing on the core scientific methods around which Euclid was designed, namely weak lensing and galaxy clustering. Specific projects include creating likelihood pipelines for galaxy clustering and weak lensing measurements, preparing a method to determine the observational mask, and defining the weak lensing calibration strategy. These areas would directly support Thomas Kitching and Will Percival, who co-lead the weak lensing and galaxy clustering science working groups respectively. We also request support for legacy science, providing support for Chris Conselice who co-leads working groups focussed on legacy science; and for Carlton Baugh who leads the mock galaxy work in the cosmological simulations working group. Travel funds are also requested: to be administered by Carlton Baugh at Durham University to allow UK scientists to attend Euclid meetings.


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Bianchi D (2017) Unbiased clustering estimation in the presence of missing observations in Monthly Notices of the Royal Astronomical Society

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Howlett C (2017) Galaxy two-point covariance matrix estimation for next generation surveys in Monthly Notices of the Royal Astronomical Society

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Kalus B (2016) Unbiased contaminant removal for 3D galaxy power spectrum measurements in Monthly Notices of the Royal Astronomical Society

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Markovic K (2017) Large-scale retrospective relative spectrophotometric self-calibration in space in Monthly Notices of the Royal Astronomical Society

Description This funding allowed my research group in the UK to prepare for the Euclid satellite mission. There were no major dicoveries, but a lot of work was done to make sure that Euclid will be a major success.
Exploitation Route They will be used when we have data from the Euclid mission.
Sectors Aerospace, Defence and Marine