Cosmic Visions Euclid Science Support

Lead Research Organisation: Durham University
Department Name: Physics


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.

Planned Impact

The principal beneficiary from this project will be the science community, through the intensive involvement of UK scientists and engineers with key and particular expertise in setting the foundations for the Euclid mission. This community will initially be those working on the nature of Dark Energy and Dark Matter, but much more extensively, the broad reach and unique nature of the Euclid means that it will be a fundamental input in the research of almost every UK astronomer in the future.

The immediate beneficiaries from this grant will be as follows:

- UK groups working in Dark Energy research, as this project will provide a focus and an application for their expertise. UK astronomy instrumentation groups will benefit from their close interaction with this science input, and from meeting the challenges in the large-scale space instrumentation that this mission demands. These science institutes and UK and European industry will benefit mutually through the close collaboration set up between them in optimising the mission and in the exchange of expertise and technological know-how.

- UK industry will also benefit by extending their expertise through being actively involved in this study/research. Longer-term benefits will arise through the UK industrial involvement in the mission - specifically the electronics for the visible plane imager- and potentially other areas.

- ESA will benefit from, and indeed will depend on, the participation and leadership of highly able UK teams, with a long track record in Dark Energy research.

- UKSA and STFC will benefit in that the investment in supporting a strong UK role in the Euclid science activities will generate significant scientific leverage in the eventual UK astronomy exploitation of the Euclid mission. Science input into the requirements process for the design of Euclid (for example the scale of the survey and its depth) will ensure that high priority science demands of UK astronomy are met.

- Besides cosmology, the potential for additional science with Euclid will benefit other areas of UK strength in astrophysics.

Beyond the scientific community, Euclid's breath-taking whole-sky multi-colour images with much better resolution than can be achieved from the ground will become ingrained in our culture, much as the iconic images from HST have done. Euclid is a space mission and every mission to date has generated considerable interest in the media. Euclid has a number of unique aspects to engage the non-specialist. The primary science goal is to find out what is behind the accelerating cosmic expansion, and to determine if Einstein's theory of gravity is wrong on large scales, this has been billed as the biggest problem in physics today and its solution will require a fundamental breakthrough. Euclid will make the ultimate map of the Universe, spanning enormous scales in length and look-back time: images from this survey will become part of the wallpaper of our culture. We believe the impact of these fundamental Euclid science outputs are potentially at the level of the impact that the search for the Higgs Boson has had in particle physics: this is at least in part responsible for a resurgence in interest in physics and STEM subjects generally.

Space science programmes are always an engine in driving space technologies (including spacecraft system analysis) in UK and cross-European industry, given their demanding targets and the analysis required to achieve and maintain performance compliance and reliability. Spacecraft system requirements: The development of the spacecraft to meet the science requirements is always a collaboration with the industry system team. The ability of space industry to meet science requirements develops capabilities and abilities to win contracts in other areas. Skill development: The Euclid Science Support will develop the skills of 4 postdoctoral staff.


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Jose C (2016) The clustering of dark matter haloes: scale-dependent bias on quasi-linear scales in Monthly Notices of the Royal Astronomical Society

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Shi D (2016) Can we distinguish early dark energy from a cosmological constant? in Monthly Notices of the Royal Astronomical Society

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Jose C (2017) Understanding the non-linear clustering of high-redshift galaxies in Monthly Notices of the Royal Astronomical Society

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Stothert L (2018) The PAU Survey: spectral features and galaxy clustering using simulated narrow-band photometry in Monthly Notices of the Royal Astronomical Society

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Cucciati O (2016) Measuring galaxy environment with the synergy of future photometric and spectroscopic surveys in Monthly Notices of the Royal Astronomical Society

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Gonzalez-Perez V (2017) The host dark matter haloes of [O II] emitters at 0.5 < z < 1.5 in Monthly Notices of the Royal Astronomical Society

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Smith A (2017) A lightcone catalogue from the Millennium-XXL simulation in Monthly Notices of the Royal Astronomical Society

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He JH (2016) Subhalo Abundance Matching in f(R) Gravity. in Physical review letters

Description This award has supported the participation of UK researchers in the preparation for the ESA mission Euclid
Exploitation Route This work is helping with the preparations for the launch and execution of the Euclid mission
Sectors Education