Neutrino Properties with Ground-Based Millimeter-Wavelength Line Intensity Mapping

TL;DR

Ground-based millimeter-wavelength line intensity mapping surveys can significantly improve constraints on neutrino properties and dark energy parameters, surpassing many current and upcoming cosmological experiments.

Contribution

This paper provides Fisher forecast analyses demonstrating the potential of upcoming LIM surveys to constrain neutrino properties and cosmological parameters more effectively than existing methods.

Findings

LIM surveys could improve constraints on $N_{\rm eff}$ and $M_\nu$ by an order of magnitude.

LIM can outperform next-generation galaxy and CMB surveys in constraining neutrino properties.

Forecasted constraints remain robust even when expanding the parameter space.

Abstract

Line intensity mapping (LIM) is emerging as a powerful technique to map the cosmic large-scale structure and to probe cosmology over a wide range of redshifts and spatial scales. We perform Fisher forecasts to determine the optimal design of wide-field ground-based mm-wavelength LIM surveys for constraining properties of neutrinos and light relics. We consider measuring the auto-power spectra of several CO rotational lines (from J=2-1 to J=6-5) and the [CII] fine-structure line in the redshift range of $0.25<z<12$. We study the constraints with and without interloper lines as a source of noise in our analysis, and for several one- and multi-parameter extensions of $\Lambda$CDM. We show that LIM surveys deployable this decade, in combination with existing CMB (primary) data, could achieve order of magnitude improvements over Planck constraints on $N_{\rm eff}$ and $M_\nu$. Compared to next-generation CMB and galaxy surveys, a LIM experiment of this scale could achieve bounds that are a factor of $\sim3$ better than those forecasted for surveys such as EUCLID (galaxy clustering), and potentially exceed the constraining power of CMB-S4 by a factor of $\sim1.5$ and $\sim3$ for $N_{\rm eff}$ and $M_\nu$, respectively. We show that the forecasted constraints are not substantially affected when enlarging the parameter space, and additionally demonstrate that such a survey could also be used to measure $\Lambda$CDM parameters and the dark energy equation of state exquisitely well.