Disentangling the effects of Doppler velocity and primordial non-Gaussianity in galaxy power spectra

We study the detectability of large-scale velocity (Doppler) effects on redshift-space galaxy clustering, by simulating galaxy surveys and combining different types of tracers of large-scale structure. We employ a set of lognormal mocks that simulate a 20.000 deg² near-complete survey up to $z=0.8$, in which each galaxy mock traces the spatial distribution of dark matter of that mock with a realistic bias prescription. We find that the ratios of the monopoles of the power spectra of different types of tracers carry most of the information that can be extracted from a multitracer analysis. In particular, we show that by employing optimal multitracer weights to compute the redshift-space power spectra it will be possible to detect Doppler effects with 3σ, while using suboptimal weights would lower this threshold below 3σ. Finally, we investigate the potential degeneracy of these effects with the (local) non-Gaussianity parameter fNL, and how large-scale Doppler contributions could be mistaken for the signatures of primordial non-Gaussianity.