Line-Intensity Mapping: Theory Review

Abstract

Line-intensity mapping (LIM) is an emerging approach to survey the Universe, using relatively low-aperture instruments to scan large portions of the sky and collect the total spectral-line emission from galaxies and the intergalactic medium. Mapping the intensity fluctuations of an array of lines offers a unique opportunity to probe redshifts well beyond the reach of other cosmological observations, access regimes that cannot be explored otherwise, and exploit the enormous potential of cross-correlations with other measurements. This promises to deepen our understanding of various questions related to galaxy formation and evolution, cosmology, and fundamental physics. Here we focus on lines ranging from microwave to optical frequencies, the emission of which is related to star formation in galaxies across cosmic history. Over the next decade, LIM will transition from a pathfinder era of first detections to an early-science era where data from more than a dozen missions will be harvested to yield new insights and discoveries. This review discusses the primary target lines for these missions, describes the different approaches to modeling their intensities and fluctuations, surveys the scientific prospects of their measurement, presents the formalism behind the statistical methods to analyze the data, and motivates the opportunities for synergy with other observables. Our goal is to provide a pedagogical introduction to the field for non-experts, as well as to serve as a comprehensive reference for specialists.

Minor typos corrected; matches the published version, with an extended list of references. 10 figures, 40 pages + references; invited by The Astronomy and Astrophysics Review. Comments are welcome. Accompanied by an update of the lim package at https://github.com/jl-bernal/lim

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Cited by in corpus (57)

• The ALMA-ALPAKA survey I: high-resolution CO and [CI] kinematics of star-forming galaxies at z = 0.5-3.5
• Probing the Blue Axion with Cosmic Optical Background Anisotropies
• Exploiting synergies between JWST and cosmic 21-cm observations to uncover star formation in the early Universe
• Median Surface Brightness Profiles of Lyman-$\alpha$ Haloes in the MUSE Extremely Deep Field
• Patchy Screening of the CMB from Dark Photons
• Testing gravity with gravitational waves $\times$ electromagnetic probes cross-correlations
• Forecasts and Statistical Insights for Line Intensity Mapping Cross-Correlations: A Case Study with 21cm x [CII]
• Searching for blue in the dark
• A multi-tracer empirically-driven approach to line-intensity mapping lightcones
• Extragalactic CO emission lines in the CMB experiments: a forgotten signal and a foreground
• Extragalactic Science with the Experiment for Cryogenic Large-aperture Intensity Mapping
• Synergizing 21 cm and sub-millimetre surveys during reionization: new empirical insights
• Unveiling cosmological information on small scales with line intensity mapping
• CONCERTO: Extracting the power spectrum of the [C II ] emission line
• Characterizing the Conditional Galaxy Property Distribution using Gaussian Mixture Models
• Efficient simulation of discrete galaxy populations and associated radiation fields during the first billion years
• Emission-line Stacking of 21cm Intensity Maps with MeerKLASS: Inference Pipeline and Application to the L-band Deep-field Data
• The deconvolved distribution estimator: enhancing reionisation-era CO line-intensity mapping analyses with a cross-correlation analogue for one-point statistics
• Dark ages, a window on the dark sector. Hunting for ultra-light axions
• SIMPLE: Simple Intensity Map Producer for Line Emission
• Characteristic Functions for Cosmological Cross-Correlations
• Towards Accurate Modeling of Line-Intensity Mapping One-Point Statistics: Including Extended Profiles
• The [C II] line emission as an interstellar medium probe in the MARIGOLD galaxies
• On the contributions of extragalactic CO emission lines to ground-based CMB observations
• Bayesian Multi-line Intensity Mapping
• $\text{slick}$: Modeling a Universe of Molecular Line Luminosities in Hydrodynamical Simulations
• Boosting Line Intensity Map Signal-to-Noise with the Ly-$\alpha$ Forest Cross-Correlation
• A Forecast for Large Scale Structure Constraints on Horndeski Gravity with Line Intensity Mapping
• A statistical framework for recovering intensity mapping autocorrelations from crosscorrelations
• The power spectrum of galaxies from large to small scales: a line-intensity mapping perspective
• Probing the cosmic web in Ly$\alpha$ emission over large scales: an Intensity Mapping forecast for DECaLS/BASS and DESI
• COMAP Pathfinder -- Season 2 results II. Updated constraints on the CO(1-0) power spectrum
• Upcoming searches for decaying dark matter with ULTRASAT ultraviolet maps
• CONCERTO at APEX -- On-sky performance in continuum
• Leveraging cross-correlations and linear covariance-based filtering for line-intensity map reconstructions at linear scales
• COMAP Pathfinder -- Season 2 results III. Implications for cosmic molecular gas content at "Cosmic Half-past Eleven"
• Relatively Fast and Reasonably Furious: Evidence for Increased Burstiness in Smaller Halos at Cosmic Dawn
• Towards a multi-tracer neutrino mass measurement with line-intensity mapping
• The Cosmic Infrared Background Experiment-2: An Intensity Mapping Optimized Sounding-rocket Payload to Understand the Near-IR Extragalactic Background Light
• [CII] luminosity models and large-scale image cubes based on COSMOS 2020 and ALPINE-ALMA [CII] data back to the epoch of reionisation
• Lyα Intensity Mapping in HETDEX: Galaxy-Lyα Intensity Cross-Power Spectrum
• Constraining $z\lesssim 2$ ultraviolet emission with the upcoming ULTRASAT satellite
• SPECTER: An Instrument Concept for CMB Spectral Distortion Measurements with Enhanced Sensitivity
• The informativeness of [C II] line-intensity mapping as a probe of the H I content and metallicity of galaxies at the end of reionization
• Constraining the halo-ISM connection through multi-transition carbon monoxide line-intensity mapping
• Removal of interloper contamination to line-intensity maps using correlations with ancillary tracers of the large-scale structure
• oLIMpus: An Effective Model for Line Intensity Mapping Auto- and Cross- Power Spectra in Cosmic Dawn and Reionization
• Superfluid-tight cryogenic receiver with continuous sub-Kelvin cooling for EXCLAIM
• Direct correlation of line intensity mapping and CMB lensing from evolution along the lightcone
• Data-driven Cosmology from Three-dimensional Light Cones
• Constraining the [CII] luminosity function from the power spectrum of line-intensity maps at redshift 3.6
• Radiative Transfer Simulations of Ly$\alpha$ Intensity Mapping During Cosmic Reionization Including Sources from Galaxies and the Intergalactic Medium
• CCAT: A status update on the EoR-Spec instrument module for Prime-Cam
• Probing the warm dark matter mass with [C II] intensity mapping
• A New Boundary Condition on Reionization
• Comparison of Cross-Correlation Methods for Line Intensity Mapping
• Unveiling the evolution of the CO excitation ladder through cross-correlation of CONCERTO-like experiments and galaxy redshift surveys