Constraining Cosmology With the CMB $\times$ LIM-Nulling Convergence

TL;DR

This paper investigates a nulling technique combining CMB and LIM lensing maps to isolate high-redshift matter distribution, enabling competitive constraints on cosmological parameters and tests beyond standard models.

Contribution

It demonstrates the effectiveness of LIM-nulling estimators for high-redshift cosmology and their potential for model-independent tests beyond $ mf extLambda$CDM.

Findings

LIM-nulling can constrain neutrino mass similarly to traditional CMB lensing.

The technique provides a clean high-redshift probe for cosmology.

It enables model-independent tests of the high-redshift universe.

Abstract

Lensing reconstruction maps from the cosmic microwave background (CMB) provide direct observations of the matter distribution of the universe without the use of a biased tracer. Such maps, however, constitute projected observables along the line of sight that are dominated by their low-redshift contributions. To cleanly access high-redshift information, Maniyar et al. showed that a linear combination of lensing maps from both CMB and line intensity mapping (LIM) observations can exactly null the low-redshift contribution to CMB lensing convergence. In this paper we explore the scientific returns of this nulling technique. We show that LIM-nulling estimators can place constraints on standard $\Lambda$CDM plus neutrino mass parameters that are competitive with traditional CMB lensing. Additionally, we demonstrate that as a clean probe of the high-redshift universe, LIM-nulling can be used for model-independent tests of cosmology beyond $\Lambda$CDM and as a probe of the high-redshift matter power spectrum.