Browsing by Author "Fonseca, Jose"

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    Hunting down horizon-scale effects with multi-wavelength surveys
    (American Astronomical Society, 2015) Fonseca, Jose; Camera, Stefano; Santos, Mario G.; Maartens, Roy
    Next-generation cosmological surveys will probe ever larger volumes of the universe, including the largest scales, near and beyond the horizon. On these scales, the galaxy power spectrum carries signatures of local primordial non-Gaussianity (PNG) and horizon-scale general relativistic (GR) effects. However, cosmic variance limits the detection of horizon-scale effects. Combining different surveys via the multi-tracer method allows us to reduce the effect of cosmic variance. This method benefits from large bias differences between two tracers of the underlying dark matter distribution, which suggests a multi-wavelength combination of large volume surveys that are planned on a similar timescale. We show that the combination of two contemporaneous surveys, a large neutral hydrogen intensity mapping survey in SKA Phase 1 and a Euclid-like photometric survey, will provide unprecedented constraints on PNG as well as detection of the GR effects. We forecast that the error on local PNG will break through the cosmic variance limit on cosmic microwave background surveys, depending on assumed priors, bias, and sky coverage. GR effects are more robust to changes in the assumed fiducial model, and we forecast that they can be detected with a signal-to-noise of about 14.
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    Synergies between intensity maps of hydrogen lines
    (Oxford University Press, 2018) Fonseca, Jose; Maartens, Roy; Santos, Mario G.
    We study synergies between Hi 21cm and Hα intensity map observations, focusing on SKA1- like and SPHEREx-like surveys. We forecast how well such a combination can measure features in the angular power spectrum on the largest scales, that arise from primordial non- Gaussianity and from general relativistic effects. For the first time we consider Doppler, Sachs-Wolfe and integrated SW effects separately. We confirm that the single-tracer surveys on their own cannot detect general relativistic effects and can constrain the non-Gaussianity parameter fNL only slightly better than Planck. Using the multi-tracer technique, constraints on fNL can be pushed down to ~ 1. Amongst the general relativistic effects, the Doppler term is detectable with the multi-tracer. The Sachs-Wolfe terms and the integrated SW effect are still not detectable.