The most recent progress in observational cosmology has led to the emergence of the so-called concordance cosmological model. This model provides an accurate description of a wide range of independent observations with a handful of adjustable parameters. However, it relies on two untested assumptions. The first of these is about the initial conditions of the Universe and the nature of gravity. The second involves the two dominant contributions to the energy density of the Universe, dark matter and dark energy. The nature of these two components is largely unknown.
Kunstners fremstilling av satellitten Euclid: ESA - C. Carreau
About the project
Dark energy is arguably the greatest mystery of the two. It is invoked to explain the accelerated expansion of the Universe at the present epoch. There is a plethora of explanations for dark energy ranging from a simple additional term in the fundamental equations of General Relativity (GR) to additional particles or fields, or that it is a signature of the break-down of GR on large distance scales. To address this problem, the precision in the observations must be improved by more than an order of magnitude.
Euclid is a survey mission scheduled for launch in 2019, and is designed to understand the origin of the accelerating expansion of the Universe. It will use cosmologic probes to investigate the nature of dark energy, dark matter and gravity by tracking their observational signatures on the geometry of the Universe and on the history of cosmic structure formation. Euclid will map the large-scale structure of the Universe over a cosmic time covering the last 10 billion years, corresponding to redshifts between 1 and 2. The mission is optimized for two independent primary cosmological probes: Weak gravitational lensing (WL) and Baryonic Acoustic Oscillations (BAO).
WL is a technique to map dark matter and measure dark energy by quantifying the apparent distortions of galaxy images caused by mass inhomogeneities along the line of sight. The lensing signal is derived from accurate measurements of the shapes and distances of galaxies.
Baryon Acoustic Oscillations
BAO are patterns imprinted in the clustering of galaxies. These patterns provide a standard ruler with which we can measure how distances increase over cosmic timescales, thereby allowing us to deduce the expansion rate at different epochs. The properties of the patterns are derived by measuring accurately the distances to galaxies.
Surveyed in the same cosmic volume, these two probes provide necessary cross-checks on systematic errors. They also provide measurements of large-scale structure via different physical fields (gravitational potential, density and velocity), which are all required for testing dark energy and gravity on all scales.
The Euclid survey also yields data for several important complimentary cosmological probes such as galaxy clusters, redshift space distortions and the Integrated Sachs Wolfe effect.
For Norwegian scientists to be able to participate in the scientific exploitation of Euclid, Norway must contribute to the consortium through contribution to Management and Coordination by providing a member of the Euclid Consortium Board (ECB) and must contribute to the instruments (VIS and NISP) and the Science Ground Segment with direct deliveries (not including scientific research).
In addition, it is vital that Norway participates in several of the many science working groups that are preparing for the analysis of data from Euclid and that Norwegian scientists engage strongly in research that will lay the ground for doing science with Euclid data when they appear after 2019.
Management and coordination
The Norwegian management consists of two parts: 1) Norwegian member of the Euclid Consortium Board, and 2) Management and coordination of the Norwegian contribution, both to instruments, science ground segment and scientifically. Per B. Lilje carries out both of these tasks.
Contribution to the NISP instrument
The NISP (Near Infrared Spectrograph and Photometer) instrument will be built in cooperation with ESA by a consortium led by the NISP Project Manager Thierry Maciaszek of CNES (Centre National d’Études Spatial), Toulouse. On contract with the Institute of Theoretical Astrophyics, CMR Prototech AS in Bergen will build mechanical parts of the NISP instrument (specifically of the NI-OMA, Opto-Mechanical Assembly and the NI-DS, Detector System) and its Mechanical Ground Support Equipment (MGSE).
Contribution to the Euclid Science Ground Segment
The Euclid Consortium will provide most of the extremely large and complicated Science Ground Segment (ESA will also provide some parts at ESAC) needed to reduce and analyse the deluge of data that will come from Euclid through a number of large Organisational Units (OU). We will participate with Common Quality Control Tools to the SGS Systems Engineering team, based on our experience from the outstanding Hinode Science Data Centre Europe, led by Stein Vidar H. Haugan.
Science activities in the implementation phase
The Euclid Mission Consortium has set up a number of science working groups (WGs) for scientific preparation of the mission. They are divided in 3 groups, Cosmology WGs (Cosmology theory, Weak lensing, Galaxy clustering, Clusters of galaxies, and CMB cross-correlations), Legacy WGs (Primeval galaxies, Galaxies and AGN evolution, Nearby galaxies, The Milky Way, Planets, and Supernovae and Transients) and finally the Cosmological Simulation WG, which is a group in itself.
David Mota leads the Norwegian scientific participation in Euclid. He and Øystein Elgarøy, as well as postdocs, participate in the Cosmology theory WG and he, with Ph.D. students and postdocs, is a major participant in the Cosmological Simulation WG. Per. B. Lilje is a member of the Galaxy clustering WG. When the very heavy effort presently done with Planck is winding down, Frode Hansen and Hans Kristian Eriksen will join the effort, especially in the CMB cross-correlations WG.
The scientific and management activities are financed by two grants from the Research Council of Norway: 208014/F50 “Norwegian Participation in Euclid: Massive Neutrinos and Dark Couplings” and 216756/F50 “Norwegian Participation in Euclid: Implementation Phase”. The development of NISP elements and the Norwegian elements of the Science Ground Segment will be funded by the Norwegian Space Centre. Minor funding is also received through several other Research Council and European Research Council grants.
Professor Licia Verde (University of Barcelona and Adjunct Professor at the Institute of Theoretical Astrophysics)
Professor Anne-Christine Davis (Department of Applied Mathematics and Theoretical Physics, University of Cambridge)
Dr. Baojiu Li (Institute for Computational Cosmology, Durham University)