Lighting up the dark side of the Universe

Lead Research Organisation: Durham University
Department Name: Physics


A series of striking observational and theoretical breakthroughs have resulted in a surprising view of the Universe in which most of its contents are dark: the bulk of the mass in the Universe is thought to be "dark matter" whilst the current dynamics of the Universe are governed by "dark energy". The astronomical community is organizing itself into large international teams to carry out the next generation of galaxy survey to understand the nature of the dark universe.

Our objective is to develop a new state of the art in mock galaxy catalogues to aid this effort. As surveys become larger to beat down random measurement errors, it is essential that we develop a better understanding of systematic effects, such as the relation between the galaxy and matter distributions, called galaxy bias. Such effects will limit the scientific potential of future surveys unless theoretical models are developed which allow them to be properly incorporated into the estimation of cosmological parameters.

Astronomy is arguably the highest profile Chilean scientific activity on the international stage. By allowing the leading Chilean researchers access to expertise in galaxy formation modelling and a national level supercomputer, this project will lay the foundations for the scientific exploitation of major new surveys, including the European Space Agency's Euclid mission and new collaborations with Europe. We will also train young Chilean researchers. The outputs of the project will include mock galaxy catalogues which will be released to the wider astronomical community through a relational database.

Planned Impact

Our goal is to develop a methodology to produce the most accurate description possible of galaxy clustering. We will extend current techniques by implementing them into much larger N-body simulations than has been attempted before and by expanding the scope of the calculations to include the non-standard models outlined above. We will also attempt to model small scale changes in the distribution of matter caused by baryonic physics, guided by the results of hydrodynamical simulations.

The scientific results of the project will be described in a number of refereed publications which will be submitted to the main, international peer reviewed journals in the subject. We anticipate that each of the objectives listed above will lead to 1-2 papers, giving 10-16 papers over the three year project. These results will also be disseminated in talks at workshops and conferences by the participants as opportunities arise. The funding of the project will be duly acknowledged in all outputs.

The calculations in our project are computationally demanding, requiring N-body simulations which can only be run on national level supercomputers. The project will provide an immediate benefit to Chilean researchers through giving them direct access to these calculations, which cannot currently be produced with the resources available at Catolica. The output of these calculations will be mirrored on the computer system at the Center for Astro Engineering, allowing efficient further postprocessing and analysis by other Chilean researchers beyond those supported directly by this project.

A major output of our project will be to release the new galaxy catalogues produced via a relational databasejavascript:WebForm_DoPostBackWithOptions(new%20WebForm_PostBackOptions("ctl00$oSaveBar$btnSave",%20"",%20true,%20"",%20"",%20false,%20true)). This novel approach to publishing scientific data has become established in astronomy due to the huge datasets produced by modern observatory and simulations. The Sloan Digital Sky Survey and Virgo Consortium are prime examples of this practice. Through serving data products in formats that can interogated using simple queries, the dissemination and exploitation of these data throughout the astronomical community has increased tremendously beyond the original project teams.

Our project will train young Chilean researchers in the simulation and modelling of galaxy formation and the analysis of the large-scale structure in the galaxy distribution. These researchers will have access to the expertise and facilities in one of the leading centres of astronomical research in Europe. They will also gain exposure on the world stage through the participation in workshops and conferences made possible through the support of this project.

Finally, our project has the potential to engage a new generation of Chilean scientists and to encourage them to study science at university level. The simulations and catalogues generated by our project naturally lend themselves to making striking visualisations and movies. A movie which UK team member Peder Norberg helped to produce, which featured on the Daily Telegraph website, showed a fly-through of the GAMA survey and has so far been seen more than 250,000 times. We the assistance of a professional journalist who specializes in science stories, who has worked with researchers at PUC, we will pursue possibilities to promote our science to the Chilean public.


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Contreras S (2015) The galaxy-dark matter halo connection: which galaxy properties are correlated with the host halo mass? in Monthly Notices of the Royal Astronomical Society

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Contreras S (2017) The evolution of the galaxy content of dark matter haloes in Monthly Notices of the Royal Astronomical Society

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Contreras S (2019) The evolution of assembly bias in Monthly Notices of the Royal Astronomical Society

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Padilla N (2019) The effect of assembly bias on redshift-space distortions 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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Troncoso-Iribarren P (2020) The better half - asymmetric star formation due to ram pressure in the EAGLE simulations in Monthly Notices of the Royal Astronomical Society

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Zehavi I (2018) The Impact of Assembly Bias on the Galaxy Content of Dark Matter Halos in The Astrophysical Journal

Description Empirical models describing the clustering of galaxies are important tools to study the information contained in surveys of galaxy positions. Our work, using computer simulations, has helped to developed our understanding of the accuracy of these models.
Exploitation Route Other researchers can use the results of our project to develop more accurate empirical models of galaxy clustering.
Sectors Other

Description This project has led to a deeper understanding of empirical methods used to describe galaxy clustering. This work used computer simulations of the formation of galaxies in dark matter halos to predict the number of galaxies hosted by halos of different mass.
First Year Of Impact 2017
Sector Other
Impact Types Cultural

Description Horizon2020 RISE
Amount € 1,350,000 (EUR)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 03/2017 
End 02/2020
Description Galaxy clustering 
Organisation Pontifical Catholic University of Chile
Country Chile 
Sector Academic/University 
PI Contribution A workshop is being held in Catolica in April 2016 as a result of this award.
Collaborator Contribution Organisation of meeting and contribution of talks
Impact Workshop
Start Year 2016