Constraining primordial non-Gaussianity via a multitracer technique with surveys by Euclid and Square Kilometre Array

Understand

We forecast future constraints on local-type primordial non-Gaussianity parameter $f_{\rm NL}$ with a photometric galaxy survey by Euclid, a continuum galaxy survey by Square Kilometre Array (SKA), and their combination.

• We derive a general expression for the covariance matrix of the power spectrum estimates of multiple tracers to show how the so-called multitracer technique improves constraints on $f_{\rm NL}$.
• In particular we clarify the role of the overlap fraction of multiple tracers and the division method of the tracers.
• Our Fisher matrix analysis indicates that stringent constraints of $\sigma (f_{\rm NL})\lesssim 1$ can be obtained even with a single survey, assuming five mass bins.