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

Abstract

We forecast future constraints on local-type primordial non-Gaussianity parameter $f_{\mathrm{NL}}$ 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 $f_{\mathrm{NL}}$. 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 $\sigma (f_{\mathrm{NL}})\lesssim 1$ can be obtained even with a single survey, assuming five mass bins. When Euclid and SKA phase 1 (2) are combined, constraints on $f_{\mathrm{NL}}$ are improved to $\sigma (f_{\mathrm{NL}})=0.61(0.50)$.

5 pages, 4 figures, v2: accepted for publication in PRD

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