Friday 14 Feb 2020Testing the standard model of cosmology using large-scale structure

Ian McCarthy - Liverpool John Moores University

Newman Red 12:30-13:30

The standard model of cosmology, the LambdaCDM model, is remarkably successful at explaining a wide range of observations of our Universe.  However, it is now being subjected to much more stringent tests than ever before, and recent large-scale structure (LSS) measurements appear to be in mild tension with its predictions.  Is this tension signalling that new physics is required?  For example, time-varying dark energy, or perhaps a modified theory of gravity?  A contribution from massive neutrinos?  Before coming to such bold conclusions we must be certain that all of the important systematic errors in the LSS tests have been accounted for.

Presently, the largest source of systematic uncertainty is from the modelling of complicated astrophysical phenomena associated with galaxy formation.  In particular, energetic feedback processes associated with star formation and black hole growth can heat and expel gas from collapsed structures and modify the large-scale distribution of matter.  Cosmological hydrodynamical simulations (are the only method which) can follow all the relevant matter components and self-consistently capture the effects of feedback.  In this talk, I will review our current understanding of the role of baryons in large-scale structure cosmology and discuss implications for the existing tension(s).  I will present new results from an ongoing ERC-funded large program of simulations, called BAHAMAS, which has been designed specifically for LSS cosmology applications.  Finally, I will summarize future prospects for exploring extensions of the standard model by combining simulations with data from upcoming surveys, such as LSST, Euclid, and CMB-S4.

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