Combinations of cosmic probes : two case studies with Planck and SDSS-III/BOSS

28.04.2017 11:30 – 12:30

Cosmological experiments imaging anisotropies of the CMB or mapping galaxies all observe the same sky, i.e. the same underlying matter density field. Therefore, their measurements are spatially correlated. Cross-correlations of various experiments provide free new information that can be used to observe new effects, to improve constraints on cosmological parameters or to mitigate systematic errors. After giving a brief overview of cross-correlation studies, I will illustrate the first two aforementioned uses by projects that used CMB data from Planck and the spectroscopic survey SDSS-III/BOSS. In the first project, we performed a joint analysis that incorporates all auto- and cross-spectra of CMB lensing and galaxy overdensity, as well as CMB temperature. I will explain the methodology and present cosmological constraints derived via MCMC analyses. In particular, we demonstrated that such a joint analysis can constrain the CDM model and extensions of it including the mass of neutrinos and the dark energy equation of state. In the second project, we measured the cross-correlation between CMB lensing and the power spectrum of the Lyman- forest. This bispectrum measures the non-linear response of small-scale fluctuations in the intergalactic medium to large-scale overdensities. While testing our understanding of the relationship between dark matter and intergalactic gaz, this observable can be used to calibrate hydrodynamical simulations.

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Bâtiment: Ecole de Physique

Salle 234, 24 quai Ernest-Ansermet

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