Constraining primordial non-Gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys
Sheean Jolicoeur, Roy Maartens, Simthembile Dlamini
Abstract
Abstract 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 21 cm intensity mapping survey, like the upcoming SKAO survey. A Fisher forecast of the precision on the local primordial non-Gaussianity parameter $$f_{\textrm{NL}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>f</mml:mi> <mml:mtext>NL</mml:mtext> </mml:msub> </mml:math> , 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 $$\sigma (f_{\textrm{NL}}) \sim 4$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>σ</mml:mi> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>f</mml:mi> <mml:mtext>NL</mml:mtext> </mml:msub> <mml:mo>)</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:math> .