Sheean, JolicoeurMaartens, RoyJolicoeur, SheeanDlamini, Simthembile2023-05-092023-05-092023Jolicoeur, S., Maartens, R., & Dlamini, S. (2023). Constraining primordial non-gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys. European Physical Journal C, 83(4) doi:10.1140/epjc/s10052-023-11482-2https://doi.org/10.1140/epjc/s10052-023-11482-2http://hdl.handle.net/10566/8906Surveys 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) ∼ 4enCosmic variancePrimordial UniverseOptical galaxy surveyPrimordial non-Gaussianity parameterArticle