Speaker
Description
Inflation offers a compelling explanation of how the primordial universe evolved into the modern $\Lambda$CDM paradigm. Measuring the non-Gaussianity of primordial density fluctuations will deliver crucial evidence for inflation and insight into its more fundamental mechanism. We forecast future constraints on local primordial non-Gaussianity ($f_{\rm NL}^{\rm loc}$) under the context of {LSST, SPHEREx}$\times$SO. This leverages the $f_{\rm NL}$-induced scale dependent bias on galaxy overdensity $\delta_g$, cross-correlated with the CMB kinetic Sunyaev-Zeldovich (kSZ) reconstructed velocity $v$ for cosmic variance cancellation. The $gg$ autospectrum at large scales suffers from data systematics in real observations, but we emphasize that removing $gg$-auto at the largest scales still yields a promising $\sigma(f_{\rm NL})$, the error bar in measuring $f_{\rm NL}^{\rm loc}$. We also briefly discuss how this constraint depends on the uncertain amplitude of the kSZ velocity signal. Finally, we compare cross-correlations between $\delta_g\times\kappa$ (CMB lensing) and $\delta_g\times v$ for constraining $f_{\rm NL}^{\rm loc}$.