Non-Gaussian halo bias and future galaxy surveys

TL;DR

This paper forecasts how upcoming galaxy surveys can detect primordial non-Gaussianity through scale-dependent halo bias, potentially revealing physics beyond simple inflation models.

Contribution

It demonstrates the potential of future surveys to measure local primordial non-Gaussianity with $|f_{NL}|$ of order unity using large-scale galaxy clustering and CMB cross-correlations.

Findings

Future surveys can detect $|f_{NL}|$ of order unity.

Large-scale structure signals can exceed predictions from simple inflation models.

Cross-correlation with CMB enhances detection sensitivity.

Abstract

We forecast constraints on primordial non-Gaussianity achievable from forthcoming surveys by exploiting the scale-dependent halo bias introduced on large scales by non-Gaussian initial conditions. We explore the performance of exploiting both the shape of the galaxy power-spectrum on large scales and the cross-correlation of galaxies with Cosmic Microwave Background maps through the Integrated Sachs Wolfe effect. We find that future surveys can detect primordial non-Gaussianity of the local form with a non-Gaussianity parameter $|f_{\rm NL}|$ of order unity. This is particularly exciting because, while the simplest single-field slow-roll models of inflation predict a primordial $|f_{\rm NL}|\ll 1$, this signal sources extra contributions to the effective $f_{\rm NL}$ of large-scale structures that are expected to be above our predicted detection threshold.