Browsing by Author "Dlamini, Simthembile"

Now showing 1 - 3 of 3
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    Constraining primordial non-Gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys
    (Institute for Ionics, 2023) Sheean, Jolicoeur; Maartens, Roy; Jolicoeur, Sheean; Dlamini, Simthembile
    Surveys of the matter distribution contain ‘fossil’ information on possible non-Gaussianity that is generated in the primordial universe. This primordial signal survives only on the largest scales where cosmic variance is strongest. By combining different surveys in a multi-tracer approach, we can suppress the cosmic variance and significantly improve the precision on the level of primordial non-Gaussianity.We consider a combination of an optical galaxy survey, like the recently initiated DESI survey, together with a new and very different type of survey, a 21cm intensity mapping survey, like the upcoming SKAO survey. A Fisher forecast of the precision on the local primordial non-Gaussianity parameter fNL, shows that this multi-tracer combination, together with non-overlap single-tracer information, can deliver precision comparable to that from the CMB. Taking account of the largest systematic, i.e. foreground contamination in intensity mapping, we find that σ( fNL) ∼ 4
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    Constraining primordial non-gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys
    (SpringerOpen, 2023) Jolicoeur, Sheean; Maartens, Roy; Dlamini, Simthembile
    Surveys of the matter distribution contain ‘fossil’ information on possible non-Gaussianity that is generated in the primordialUniverse. This primordial signal survives only on the largest scales where cosmic variance is strongest. By combining different surveys in a multi-tracer approach, we can suppress the cosmic variance and significantly improve the precision on the level of primordial non-Gaussianity.We consider a combination of an optical galaxy survey, like the recently initiated DESI survey, together with a new and very different type of survey, a 21cm intensity mapping survey, like the upcoming SKAO survey.
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    Using skao and other surveys to study the large-scale structure of the universe
    (Universty of the Western Cape, 2024) Dlamini, Simthembile; Maartens, Roy
    We are currently in a time of precision cosmology, marked by an extensive accumulation of data for comprehending our Universe. Nonetheless, our current grasp of the subject remains incomplete. Our most successful cosmological model relies on components that have yet to be directly detected and do not harmonize with our broader physics model. This implies that there is still much to probe and a high demand for novel techniques to explore the cosmos. One method gaining traction over the last decade is mapping the intensity of the 21cm emission from neutral hydrogen (HI) within unresolved galaxies. Understanding the large-scale structure of the Universe, characterized by galaxies, clusters, and superclusters, is a cornerstone of modern astrophysics. This research presents an investigation into the Universe’s large-scale structure, employing the Square Kilometre Array Observatory (SKAO) in conjunction with other surveys. The study leverages the analytical tool of Fisher forecast analysis to estimate the constraining power of these surveys. The SKAO offers a unique opportunity to probe the Universe’s large-scale structure via the 21 cm emission line of HI. By incorporating complementary surveys, this research develops a multi-tracer view of cosmic structure, encompassing various redshift ranges and investigating the constraints on key cosmological parameters.