Norwegian Participation in Euclid: Implementation phase, part 3

Cosmology, the study of the Universe as a whole, has come a long way in the last twenty years, mainly because of observatories, like the satellite Planck, which have studied the Cosmic Microwave Background radiation coming from the Big Bang, and galaxy surveys, like 2dF, SDSS and DES, which have mapped the distribution of galaxies in the Universe. This has given us a model, called the Standard Model, or LCDM, where most of the parameters are determined with a precision unthinkable 20 years ago. However, there are three major issues with the Standard Model. First, it postulates that ordinary matter, made of protons, neutrons and electrons, only make up 16% of the matter density in the Universe. The remaining 84% consists of something called Cold Dark Matter, which we don't know what is. Secondly, it postulates that the Big Bang started with a so-called inflation phase, when the Universe expanded at an incredible rate. There are many possible theories for inflation, but so far they have few observational constrains. Most mystical at all, in the Standard Model, only 31% of the total energy density in the University is in the form of matter in any form, 69% consists of what we call Dark Energy, which is understood even less than the Dark Matter. However, it is needed to understand the accelerated expansion of the Universe. The satellite Euclid, which was launched by the European space agency ESA in July 2023, attacks all these three problems, and especially the problem of the Dark Energy. By studying the shapes of billions of galaxies and by measuring the radial velocity of about one hundred million galaxies, it maps the expansion rate of the Universe as a function of time with high accuracy. This project financed, in addition to managerial participation in the Euclid consortium, research that has enabled Norwegian scientists to have a leading role in the analysis of the data from Euclid when they are now appearing. In the period 2021 to 2024, a large number of articles from this preparatory research has been published with Norwegian co-authors, including many based on data from the Dark Energy Survey (DES), where postdoc Ismael Ferrero is "builder". Ph.D. student Renate Mauland-Hus implemented and tested an approach to treating massive neutrinos in simulations with modified gravity, as part a code comparison project within Euclid for simulations with massive neutrinos, with very good results. The article, with Mauland-Hus in the group of lead authors, was published in Adamek et al., JCAP (2023). She has led research (Mauland, Elgarøy, Mota & Winther, A&A, 2023) testing how statistics of voids in the galaxy distribution can distinguish between massive neutrinos and modified gravity. Furthermore, she led the development of a method utilizing artificial intelligence to learn from simulations to distinguish modified gravity models from the LCDM model using the power spectrum determined by Euclid (Mauland, Winther & Ruan, A&A, 2024). These three articles constitutes her Ph.D. thesis, that she successfully defended in December 2023. Postdoc Ismael Ferrero has made the mock galaxy catalogues (Ferrero et al. 2021, A&A) which are used in the analysis of the third year DES data and the method was further developed for Euclid during his one-year stay abroad at Instituto de Astrofísica de Canarias. He implemented modified gravity in the Bias Assignment Method (BAM) for use by Euclid, and tested this on data from the Dark Energy Spectroscopic Instrument (DESI). Ph.D. student Sladana Radinovic (funded by the University of Oslo, but attached to this project) led, together with others in the group, a project that studied how Euclid can test the general theory of relatively with "cosmic voids". The results are highly interesting and have been published by the Euclid consortium in 2023 in a paper with 121 co-authors (Radinovic et al. 2023, A&A). She defends her Ph.D. on the 29th of November, 2024. The integration of the instruments VIS and NISP (where UiO and Clara Venture Labs delivered important parts of the NISP instrument) was completed and Euclid was launched on the 1st of July, 2023, by a Falcon 9 launcher from Cape Canaveral. It got into the correct orbit around the Earth-Sun 2nd Lagrange point, but three problems of the spacecraft were soon found. Fortunately these have now been mitigated, and after tests and lengthy calibrations, Euclid started its 6.5 year long survey in February 2024. The group organized the Euclid Consortium Meeting 2022 in Oslo April 25 - 29, 2022. Although the meeting was in hybrid format, more than 300 Euclid consortium members attended in person (and about 300 remotely). The meeting, which was the first physical annual consortium meeting after the pandemic started, was a huge success.

Den rent vitenskapelige virkningen av prosjektet er at det har utviklet og testet metoder for å analysere data fra galakse-"surveys", og spesielt Euclid, for å kunne teste alternative gravitasjonsteorier. Disse metodene vil nå bli anvendt av Euclid-konsortiet på de virkelige dataene. Det første årets data, februar 2024 - februar 2025, vil etter kalibreringer etc. gjøres tilgjengelig internt i konsortiet i juni 2025, og de første kosmologiske resultater fra disse vil publiseres i juni 2026. For prosjektets deltagere har dette gitt kompetanse som muliggjør ledende posisjoner i arbeidsgruppene innen Euclid-konsortiet. Det åpner også for forskning og forskingsledelse videre fremover. Ved Institutt for teoretisk astrofysikk har prosjektet også gitt nærmere samarbeid mellom kosmologer og ekstragalaktiske astrofysikere innen numeriske simuleringer. Prosjektet har finansiert en postdoktor og en stipendiat, og en stipendiat finansiert av UiO har vært tilknyttet prosjektet. Postdoktoren (fra Argentina) har etter fullført prosjekt valgt å bli i Norge utenom akademia, som Market Risk Analyst i Statkraft, og har dermed tilført hjernekraft til norsk næringsliv. Den ene stipendiaten har etter fullført PhD også gått over i næringslivet som astrofysiker og data analyst i Time and Date AS. Den andre stipendiaten fortsetter etter fullført PhD forskningen i Euclid-konsortiet som postdoktor ved Institute of Space Sciences (ICE-CSIC) i Spania. Euclid-prosjektet i Norge har, finansiert av ESAs PRODEX-program (ca. 25 mill. kroner), i tett tilknytning til dette prosjektet, hatt nært samarbeid med norsk industri gjennom Clara Venture Labs AS som har konstruert og bygget vesentlige deler av NISP-instumentet på Euclid. Dette har gitt ny kompetanse til bedriften som de utnytter i nye rom-kontrakter. Det har også gitt muligheter for samarbeid mellom forskere ved Institutt for teoretisk astrofysikk og industri om nye prosjekter i fremtiden.

One of the most outstanding problems in physics and astrophysics today is the existence of dark energy, which is inferred from the apparent accelerated expansion of the universe. Dark energy is believed to comprise about 70% of the energy content of the universe today, however, it's nature is largely unknown. The simplest model is to assume that the dark energy is in the form of a cosmological constant. There are, however, good reasons to believe that the nature of the dark energy could be more complicated than this. Euclid is an M-class mission with a targeted launch in 2022. Its primary objective is to study dark energy, secondary objectives are covering most of cosmology and astrophysics. The main observational targets will be baryonic acoustic oscillations and weak lensing measurements. Euclid was by ESA in 2011 selected as the third M mission in the Cosmic Vision programme, and it was adopted in 2012. This proposal is first of all for, coordinated by the Euclid Cosmological Simulations and Cosmological Theory Science Working Groups, studying the evolution of non-linear structures in the universe in a class of interesting cosmological models with modified gravity, and with massive neutrinos, baryonic physics and non-gaussian initial conditions. This research project will already give significant constraints on such models when compared with existing data, but will especially give interesting forecasts for how Euclid data best can give constraints. Furthermore, the project will build competence in numerical simulations of growth of structure in non-standard cosmological models, something that will be essential in future Euclid research. Furthermore, the project will give necessary funding of management and coordination of the Norwegian participation in Euclid (the direct costs of Norwegian contributions to instruments and science ground segment are funded by the the Norwegian Space Centre through the PRODEX programme of ESA).