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Power of multi-tracing to access the largest cosmic scales

Josť Carlos Fonseca
Padova University

Next-generation cosmological surveys will probe ever larger volumes of the Universe, including the largest scales, near and beyond the horizon, as well as in different parts of the spectrum. On these scales, signatures of local primordial non-Gaussianity (PNG) and horizon-scale General Relativistic (GR) effects can be found in the power spectrum. However, cosmic variance limits their detection but combining different surveys via the multi-tracer (MT) method allows us to beat down cosmic variance. In addition, new ways of tracing the distribution of Cold Dark Matter, such as intensity mapping (IM), open whole new windows for potential future cosmological surveys. These will tomographically probe large volumes of the universe creating unprecedented synergies between the electro-magnetic spectrum. We will start by revising initial conditions from inflation as well as what we mean by GR effects in the observed power spectrum. We will then explore the concepts behind IM and the MT technique. We follow by presenting forecasts for combinations of contemporaneous surveys that can provide unprecedented constraints on PNG, potentially achieving σ(fNL) below 1, as well as a detection of the GR effects with high accuracy. In particular a large neutral hydrogen IM survey in SKA Phase 1 and a Euclid-like or a LSST-like photometric survey, will achieve σ(fNL)≃ 1.3−0.67. We will then discuss technical challenges about the implementation of the multi-tracer technique ad how to deal with them. We will finish by presenting a systematic study of different emission lines from galaxies and their potential for IM. We identify Lyα, Hα, OII, CII and the lowest rotational CO lines as the more promising ones for cosmological studies of the post reionization epoch. We will then use reasonable experimental setups from current, planned or proposed experiments to assess the detectability of the 3D power spectrum of each emission line.

2019 March 26, 14:30

Faculdade de CiÍncias da Universidade de Lisboa (C8.6 Meetings Room)
Campo Grande, 1749-016 Lisboa

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia