PUSHING THE LIMITS OF IMAGING GALAXY SURVEYS: COSMOLOGY AND ASTROPHYSICS AT HIGHER REDSHIFTS

THE STANDARD COSMOLOGICAL MODEL PROVIDES A CONSISTENT PHYSICAL PICTURE OF OUR UNIVERSE BUT REQUIRES THE ADDITION OF TWO MAIN COMPONENTS OF UNKNOWN NATURE AND ORIGIN: DARK MATTER AND DARK ENERGY. FURTHERMORE, AS THE STATISTICAL POWER OF COSMOLOGICAL EXPERIMENTS APPROACHES PERCENT-LEVEL PRECISION, OBSERVATIONS OF OUR UNIVERSE AT VERY EARLY AND LATE TIMES SHOW DISCREPANT PICTURES OF ITS EVOLUTION WITHIN THE STANDARD COSMOLOGICAL MODEL. THIS UNKNOWN NATURE AND ORIGIN OF DARK MATTER AND DARK ENERGY, TOGETHER WITH THOSE OBSERVATIONAL DISCREPANCIES, OPEN UP THE POSSIBILITY TO RESOLVE THE INCONSISTENCIES BETWEEN THE OBSERVATIONS OF THE EARLY AND LATE UNIVERSE WITH NEW PHYSICS BEYOND THE STANDARD MODEL. THE GOAL OF THIS PROPOSAL IS TO PROVIDE ROBUST COSMOLOGICAL AND ASTROPHYSICAL CONSTRAINTS IN THE REGIME THAT LIES IN BETWEEN THE EARLY AND LATE EPOCHS THAT SOURCE THE CURRENT TENSIONS IN THE COSMOLOGICAL MODEL OF THE UNIVERSE. THAT EPOCH IS THE REGIME AT INTERMEDIATE AND HIGH REDSHIFTS, WHICH IS NOT ONLY KEY TO DEPICT A COHERENT PICTURE FOR THE EVOLUTION OF THE UNIVERSE, BUT ALSO TO UNDERSTAND THE FORMATION OF STARS AND GALAXIES. IN THE PAST, THE PRECISE CHARACTERISATION OF THE LARGE-SCALE STRUCTURE IN THAT EPOCH WAS NOT POSSIBLE, AS THE GALAXY POPULATIONS FROM THAT PERIOD WERE TOO FAINT TO BE OBSERVED RELIABLY. NOW, WITH THE CURRENT AND NEW GENERATION OF GALAXY SURVEYS AND IMPROVED ANALYSIS METHODS, IT IS TIME TO PROBE THIS UNEXPLORED PERIOD IN THE EVOLUTION OF THE UNIVERSE. TO PROVIDE STATE-OF-THE-ART COSMOLOGICAL AND ASTROPHYSICAL CONSTRAINTS ON THAT PERIOD OF THE HISTORY OF THE UNIVERSE, THE PROJECT WILL USE HIGH-REDSHIFT GALAXY SAMPLES FROM THE DARK ENERGY SURVEY (DES) THAT WILL THEN BE CROSS-CORRELATED WITH MAPS OF THE WEAK GRAVITATIONAL LENSING OF THE CMB AND MAPS OF THE COSMIC INFRARED BACKGROUND (CIB) AND THERMAL SUNYAEV-ZELDOVICH (TSZ) EFFECT, FROM EXPERIMENTS SUCH AS THE SOUTH POLE TELESCOPE (SPT) AND THE ATACAMA COSMOLOGY TELESCOPE (ACT). A NEW, PIONEERING HIGH-REDSHIFT GALAXY SAMPLE DEVELOPED BY THE PI USING DES YEAR 3 DATA WILL BE THE STARTING POINT OF THE PROJECT, AND NEW GALAXY SAMPLES WILL BE DEVELOPED WITH FINAL DES DATA AND EARLY LSST OBSERVATIONS. THE COMBINATION OF GALAXY CLUSTERING AND CMB LENSING WILL PROVIDE CONSTRAINTS ON THE AMPLITUDE OF MATTER FLUCTUATIONS AT HIGH REDSHIFT, WHICH WILL BE CRUCIAL FOR UNDERSTANDING THE GROWTH OF STRUCTURES IN THAT HIGH-REDSHIFT PERIOD. THE CROSS-CORRELATIONS WITH CIB AND TSZ MAPS WILL PROVIDE CONSTRAINTS ON STAR FORMATION RATES AT AN EPOCH WHERE IT PEAKS IN THE HISTORY OF THE UNIVERSE, AND WILL ALSO BE USED TO STUDY THE IMPACT OF BARYONIC PHYSICS IN THE ANALYSIS OF MATTER FLUCTUATIONS FROM WEAK GRAVITATIONAL LENSING. IN THIS WAY, THE USAGE OF VARIOUS CROSS-CORRELATIONS BETWEEN DIFFERENT PROBES WILL ALLOW US TO ACCOUNT FOR ALL INTERDEPENDENCIES BETWEEN ASTROPHYSICAL AND COSMOLOGICAL EFFECTS. THE TIME IS PERFECT FOR THIS VENTURE: THE DES SURVEY, CURRENTLY THE MOST POWERFUL IMAGING SURVEY DATA SET, IS ANALYSING ITS FINAL DATA, AND THE RUBIN LSST, ITS NATURAL SUCCESSOR, WILL START TAKING DATA IN THE NEXT YEAR. CMB EXPERIMENTS ARE ALSO THRIVING, WITH PLANCK, SPT AND ACT ALREADY AVAILABLE AND THE SIMONS OBSERVATORY COMING SOON. THE PI OF THIS PROPOSAL PLAYS A LEADING ROLE IN THE FIELD OF WEAK LENSING COSMOLOGY AS WELL AS IN DES, AND THE WORK TEAM COMPRISES A GROUP OF CLOSE COLLABORATORS WITH COMPLEMENTARY, WORLD-CLASS EXPERTISE IN THE TOPICS AND ANALYSIS METHODS RELATED TO THE PROPOSAL.