Precision cosmology from early and late-time surveys.

Lead Research Organisation: CARDIFF UNIVERSITY
Department Name: School of Physics and Astronomy

Abstract

The cosmological quest is mainly fed by the curiosity to know how things started and evolved in time, which particular process led to the objects we see in the sky (e.g., galaxies and clusters of galaxies), where they come from and why they are moving away from us.

A key aspect of physics of the early Universe is the theory and the observation of the cosmic microwave background radiation (CMB) temperature fluctuations and polarisation. The use of the CMB to study the particle and energy content of the Universe as well as its evolution is a remarkable success of modern cosmology.
The CMB is the most ancient light we can observe in the Universe. It was born in the early Universe a few seconds after the Big Bang and thermalised in the primordial 'cosmic soup' where the high Universe temperature coupled light together with other particles. It then decoupled and was released when the Universe cooled down and the first light elements started to form (e.g., hydrogen and helium), leaving CMB photons free to escape. The CMB then provides us with a snapshot and unique view of the transparent Universe. It has been free to travel from the decoupling moment to today and it reaches us as a faint radiation with microwave wavelengths. The way it propagates and its statistical properties inform us about the physics of the early Universe (looking back in time from decoupling) and describes its particle/energy content and evolution (looking forward in time from decoupling). The statistics of the CMB temperature variations have now been measured with extreme precision over a broad range of scales, leading to a concordance standard model of cosmology. However, the standard cosmological model arising today relies on observational evidence for components and processes with unknown theoretical interpretation. We measure that 95% of the Universe is dominated by 'dark' components but we don't know yet what their nature is. We call 'dark matter' the component responsible for the galaxies formation and 'dark energy' the force opposing gravity and driving the Universe in an accelerating expansion, all this assuming that the laws of gravity are correct on all scales. We also need to invoke a super-luminal expansion in the first fraction of a second after the Big Bang to account for the homogeneity of the Universe on cosmic scales and its flatness. In the last ten years CMB data has become the most competitive and tantalising source of information to address these open theoretical issues.

My project relies on two kinds of observations complementing current data in the next decade: improved measurement of CMB polarisation and the measurement of galaxies statistics and distribution on the largest physical scales (e.g., galaxy clusters, voids, filaments, bubbles) over a broad cosmic epoch.
At the end of 2013 and early 2014 the new measurements of CMB polarisation from gound-based experiments have kicked off a new era in CMB physics. CMB polarisation will inform our understanding of the brief expansion phase of the early Universe (called cosmic inflation), probing high energy scales not testable in laboratories, and will map the gravitational potential field defining the geometry, evolution and content of the Universe. CMB polarisation is particularly effective for studying the masses of primordial neutrinos, still unmeasured today.
Current and future probes of the Universe large-scale structure, via galaxy surveys, will be instead effective in characterising the dark sector and testing the gravity laws on cosmic scales.
The combination of CMB and galaxy surveys will increase the fidelity of the cosmological reconstructions, reducing systematics and probing many cosmic epochs (the CMB gives us a snapshot of a ~400,000 years old Universe while galaxy surveys probe the last 10 billion years).

Publications

10 25 50
 
Description This award supported new astrophysical and cosmological results from the Planck satellite mission and the Atacama Cosmology Telescope.
Exploitation Route This work has sparkled new collaborations, as well as the design of new observatories and space missions. Tools released within this award are used by the global cosmology community.
Sectors Education

 
Description Training new generations of data analysts and engagement with school for promoting STEM subjects.
Sector Digital/Communication/Information Technologies (including Software),Education
Impact Types Cultural

Societal

 
Description (CMB-INFLATE) - Advanced Methodologies for Next Generation Large Scale CMB Polarization Analysis
Amount € 1,564,000 (EUR)
Funding ID 101007633 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 09/2021 
End 09/2025
 
Description (CMBforward) - A programme for cosmology from current and next-generation Cosmic Microwave Background experiments
Amount € 1,915,814 (EUR)
Funding ID 849169 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 03/2020 
End 03/2025
 
Description A Programme of Technology, Astrophysics and Cosmology in Cardiff 2019-22
Amount £2,542,358 (GBP)
Funding ID ST/S00033X/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Public
Country United Kingdom
Start 03/2019 
End 03/2022
 
Title Planck plik_lite likelihood 
Description CMB-only likelihood for the Planck mission legacy release. 
Type Of Material Improvements to research infrastructure 
Year Produced 2019 
Provided To Others? Yes  
Impact New likelihood software to analyse the Planck legacy CMB power spectra after marginalisation over other sources of emission. 
URL https://pla.esac.esa.int/#cosmology
 
Description ACT 
Organisation Princeton University
Country United States 
Sector Academic/University 
PI Contribution I am a science team member of the Atacama Cosmology Telescope. For this experiment I lead characterization and cosmological interpretation of cosmic microwave data.
Collaborator Contribution ACT is a ground-based telescope, located in Chile, in the Atacama desert. The Collaboration consists of many teams, including instrumentalists and data analysis and theory experts, working together on different aspects of the mission. I work at the end of the pipeline, needing access to the data.
Impact ACT is one of the leading experiments in cosmology, providing increasingly accurate data to understand the physics of the early universe. Since 2011, when I first joint the ACT Collaboration, ACT has delivered: -- new methodology to characterise small-scale temperature data in the microwave; -- first measurement of small-scale CMB polarisation; -- state-of-the-art constraints on cosmology from small-scale temperature, including limits on the neutrino number and mass and parameters characterising inflation; -- first evidence of CMB halo lensing (at 3sigma) using SDSS-BOSS galaxies; -- kSZ detections from different CMB-galaxy cross-correlations. Since the award of this fellowship I have participated to 5 ACT papers.
Start Year 2011
 
Description Simons Observatory 
Organisation Simons Observatory
Country Chile 
Sector Academic/University 
PI Contribution I am a member of the Simons Observatory Theory and Analysis Committee as well as a developer of the analysis pipeline for its Large Aperture Telescope.
Collaborator Contribution This is an International Collaboration of 10 countries, including more than 40 institutions and more than 106 researchers working together to build new telescopes and explore new theoretical regimes. The construction of the Observatory is funded by the Simons and Heising-Simons foundations and with contribution from the US lead institutions.
Impact The Simons Observatory is a next generation CMB experiment and will drive major advances in cosmology from 2021.
Start Year 2016
 
Description The Large Synoptic Survey Telescope 
Organisation The LSST Collaboration
Sector Academic/University 
PI Contribution I am a full member of the LSST Dark Energy Science Collaboration and one of the LSST:UK Principal Investigators, contributing to the development of the Theory and Joint Probes work.
Collaborator Contribution LSST is an international collaboration consisting of more than one hundred astronomers, physicists, and engineers spanning the globe, busy building both the instrument and the analysis pipeline.
Impact From the LSST website: "The goal of the Large Synoptic Survey Telescope (LSST) project is to conduct a 10-year survey of the sky that will deliver a 500 petabyte set of images and data products that will address some of the most pressing questions about the structure and evolution of the universe and the objects in it. The LSST survey is designed to address four science areas: • Understanding the Mysterious Dark Matter and Dark Energy • Hazardous Asteroids and the Remote Solar System • The Transient Optical Sky • The Formation and Structure of the Milky Way"
Start Year 2014
 
Title ACTPol DR4 likelihood 
Description New likelihood to distribute and utilize the power spectra data from the Atacama Cosmology Telescope polarimeter 4th data release. 
Type Of Technology Software 
Year Produced 2020 
Open Source License? Yes  
Impact This is the software released to the community to extract cosmological information from the latest Atacama Cosmology Telescope data, including observations during 2013-2016. 
URL https://lambda.gsfc.nasa.gov/product/act/act_dr4_likelihood_get.cfm
 
Description ACT DR4 press release, BBC Science and Nature interviews 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Interviews with BBC News and Nature about the new cosmological results from the Atacama Cosmology Telescope 4th data release.
Year(s) Of Engagement Activity 2020
URL https://www.bbc.co.uk/news/science-environment-53420433
 
Description Cardiff Sixth Form College and Advanced Research Computing at Cardiff 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Other audiences
Results and Impact Talk about cosmology to Sixth Form A-level students and physics teacher. Talk at ARCCA to supercomputing staff members.
Year(s) Of Engagement Activity 2019,2020
 
Description Cheltenham Science Festival 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Panel member at the event "The Universe: What Don't We Know" at the Cheltenham Science Festival.
Year(s) Of Engagement Activity 2017
URL https://www.cheltenhamfestivals.com/science
 
Description Cheltenham Science Festival 2018 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Panel member at the event "Beyond Einstein: The Future of Physics" at the Cheltenham Science Festival.
Year(s) Of Engagement Activity 2018
URL https://www.cheltenhamfestivals.com/science
 
Description Guest Speaker at the UK National Contact Point and Greenwich European Research Council Starting Grant webinars 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Guest Speaker at webinars guiding applications for the ERC Starting Grants.
Year(s) Of Engagement Activity 2021
 
Description Interviews for Nature Astronomy and New Scientist Magazine 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Interviews on CMB cosmology post-Planck and future science goals.
Year(s) Of Engagement Activity 2018,2019
 
Description Invited seminar at major conferences: ECMB, Cosmo19, LiteBIRD Symposium 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Invited seminar at the European CMB meeting in Florence and participation to the discussion of the European coordination of the CMB programme, invited talk at Cosmo19, invited talk at the LiteBIRD Symposium at the Japanese Space Agency.
Year(s) Of Engagement Activity 2017,2019
 
Description Invited seminars and Colloquia at Durham, Stockholm, Cambridge, Royal Astronomical Society Institute of Physics Cosmology day, Tenerife, Rome, Queen Mary College London 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Invited seminars and colloquia at physics and astrophysics department to present my research. For each event ~20-40 people including undergraduate and graduate students, faculty and staff members, were present.
Year(s) Of Engagement Activity 2018,2019,2020
 
Description Lecture ad the SIGRAV Cosmology School 2022 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Lecture on "Cosmic Microwave Background phenomenology" closing a PhD School in cosmology.
Year(s) Of Engagement Activity 2022
 
Description Plenary talk at the SOC of the XVI Chilean Astronomical Society (SOCHIAS) meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Plenary talk on "The Atacama desert's view of the microwave sky"
Year(s) Of Engagement Activity 2020
URL https://sochias.cl/reunion2020/
 
Description Podcast with The Guardian 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Podcast on the Hubble constant
Year(s) Of Engagement Activity 2020
URL https://www.theguardian.com/science/audio/2020/aug/06/the-fight-over-the-hubble-constant-podcast
 
Description Talk for the Guilford Astronomical Society 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Invited talk on my research "The Atacama Desert's view of the microwave sky" for the members of the Guildford Astronomical Society
Year(s) Of Engagement Activity 2022