Spectral Line De-confusion in an Intensity Mapping Survey

TL;DR

This paper introduces a method to distinguish and extract large-scale structure signals from different emission lines in intensity mapping data, effectively separating high-redshift [CII] signals from low-redshift CO interlopers.

Contribution

The paper presents a novel anisotropic power spectrum technique to separate emission lines at different redshifts within a three-dimensional intensity mapping data cube.

Findings

Successful extraction of [CII] and CO power spectra in simulations

Method effective with modest noise levels and survey geometries

Potential for improved line intensity mapping experiments

Abstract

Spectral line intensity mapping has been proposed as a promising tool to efficiently probe the cosmic reionization and the large-scale structure. Without detecting individual sources, line intensity mapping makes use of all available photons and measures the integrated light in the source confusion limit, to efficiently map the three-dimensional matter distribution on large scales as traced by a given emission line. One particular challenge is the separation of desired signals from astrophysical continuum foregrounds and line interlopers. Here we present a technique to extract large-scale structure information traced by emission lines from different redshifts, embedded in a three-dimensional intensity mapping data cube. The line redshifts are distinguished by the anisotropic shape of the power spectra when projected onto a common coordinate frame. We consider the case where high-redshift [CII] lines are confused with multiple low-redshift CO rotational lines. We present a semi-analytic model for [CII] and CO line estimates based on the cosmic infrared background measurements, and show that with a modest instrumental noise level and survey geometry, the large-scale [CII] and CO power spectrum amplitudes can be successfully extracted from a confusion-limited data set, without external information. We discuss the implications and limits of this technique for possible line intensity mapping experiments.