Phase-space Spectral Line Deconfusion in Intensity Mapping
Line intensity mapping (LIM) is a promising tool to efficiently probe the three-dimensional large-scale structure by mapping the aggregate emission of a spectral line from all sources that trace the matter density field. Spectral lines from different redshifts can fall in the same observed frequency and be confused, however, which is a major challenge in LIM. In this work, we develop a line deconfusion technique in map space capable of reconstructing the three-dimensional spatial distribution of line-emitting sources. If multiple spectral lines of a source population are observable in multiple frequencies, using the sparse approximation, our technique iteratively extracts sources along a given line of sight by fitting the LIM data to a set of spectral templates. We demonstrate that the technique successfully extracts sources with emission lines present at a few σ above the noise level, taking into account uncertainties in the source modeling and presence of continuum foreground contamination and noise fluctuations. As an example, we consider a Tomographic Ionized-carbon Mapping Experiment/CarbON C II line in post-rEionisation and ReionisaTiOn epoch (TIME/CONCERTO)-like survey targeting [C II] at the epoch of reionization, and reliably reconstruct the 3D spatial distribution of the CO interlopers and their luminosity functions at 0.5 ≾ z ≾ 1.5. We also demonstrate a successful deconfusion for the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) mission in the near-infrared wavelengths. We discuss a formalism in which the reconstructed maps can be further cross-correlated with a (galaxy) tracer population to estimate the total interloper power. This technique is a general framework to extract the phase-space distribution of low-redshift interlopers, without the need of external information, for any line deconfusion problem.
Additional Information© 2020 The American Astronomical Society. Received 2020 May 10; revised 2020 August 11; accepted 2020 August 16; published 2020 October 1. We are grateful for the helpful discussions with Chun-Lin Liu, Patrick Breysse, Matthieu Béthermin, Emmanuel Schaan, Matt Orr, the TIME collaboration, the Caltech ObsCos group, and the participants of the conference "Lines in the Large Scale Structure." We would like to thank the anonymous referee for valuable comments that improved the manuscript. Part of the research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Published - Cheng_2020_ApJ_901_142.pdf
Submitted - 2005.05341.pdf