Line intensity mapping with [CII] and CO(1-0) as probes of primordial non-Gaussianity

TL;DR

This paper investigates how future [CII] and CO intensity mapping surveys can constrain primordial non-Gaussianity, especially the local shape, by analyzing survey design, redshift coverage, and multi-tracer approaches.

Contribution

It evaluates the potential of upcoming intensity mapping surveys to measure primordial non-Gaussianity and explores optimal survey parameters and multi-tracer strategies.

Findings

Redshift coverage of at least an octave is crucial for significant constraints.

Surveys covering z~2-8 are most effective for local PNG.

Multi-tracer analysis with HI, CO, and [CII] enhances constraints.

Abstract

Constraints on primordial non-Gaussianity (PNG) will shed light on the origin of primordial fluctuations and the physics of the early universe. The intensity mapping technique is a promising probe of structure formation on large scales; at high redshifts, it can provide complementary information to other cosmological probes. We explore the potential of future wide-field [CII] and CO intensity mapping surveys in constraining PNG of the local shape, which induces a distinct, scale-dependent correction to the line bias. We explore the parameter space of CO and [CII] survey designs that can achieve the nominal target of $\sigma(f_{\rm NL}^{\rm loc}) =1$ and further calculate what constraints such surveys can place on PNG of the equilateral, orthogonal, and quasi-single field shapes. We further test the dependence of these constraints on various model assumptions; namely the halo mass function, modeling of line bias, and correlation between mass and [CII]/CO luminosity. We find that the ability of CO and [CII] intensity mapping surveys to constrain $f_{\rm NL}^{\rm loc}$ relies heavily on the spectral (redshift) coverage, requiring at least a coverage of an octave in frequency, to produce significant results, with the optimized surveys generally covering between $z\sim[2-8]$. As this redshift window partially overlaps with 21-cm EoR experiments like the Hydrogen Epoch of Reionization Array (HERA), we additionally explore the prospects for a hypothetical set of surveys to place constraints on $\sigma(f_{\rm NL}^{\rm loc})$ utilizing multi-tracer analysis between the lines of HI, CO, and [CII].