A model of spectral line broadening in signal forecasts for line-intensity mapping experiments

Abstract

Line-intensity mapping observations will find fluctuations of integrated line emission are attenuated by varying degrees at small scales due to the width of the line emission profiles. This attenuation may significantly impact estimates of astrophysical or cosmological quantities derived from measurements. We consider a theoretical treatment of the effect of line broadening on both the clustering and shot-noise components of the power spectrum of a generic line-intensity power spectrum using a halo model. We then consider possible simplifications to allow easier application in analysis, particularly in the context of inferences that require numerous, repeated, fast computations of model line-intensity signals across a large parameter space. For the CO Mapping Array Project (COMAP) and the CO(1-0) line-intensity field at $z\sim 3$ serving as our primary case study, we expect a $\sim 10\%$ attenuation of the spherically averaged power spectrum on average at relevant scales of $k\approx 0.2$-$0.3$ Mpc${}^{-1}$, compared to $\sim 25\%$ for the interferometric Millimetre-wave Intensity Mapping Experiment (mmIME) targeting shot noise from CO lines at $z\sim 1$-$5$ at scales of $k\gtrsim 1$ Mpc${}^{-1}$. We also consider the nature and amplitude of errors introduced by simplified treatments of line broadening, and find that while an approximation using a single effective velocity scale is sufficient for spherically-averaged power spectra, a more careful treatment is necessary when considering other statistics such as higher multipoles of the anisotropic power spectrum or the voxel intensity distribution.

24 pages + appendix and bibliography (33 pages total), 16 figures, 2 tables; accepted for publication in ApJ

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Cited by in corpus (21)

• Line-Intensity Mapping: Theory Review
• COMAP Early Science: I. Overview
• COMAP Early Science: V. Constraints and Forecasts at $z\sim 3$
• Precision Tests of CO and [CII] Power Spectra Models against Simulated Intensity Maps
• COMAP Early Science: VII. Prospects for CO Intensity Mapping at Reionization
• An Intensity Mapping Constraint on the CO-Galaxy Cross Power Spectrum at Redshift ~ 3
• COMAP Early Science: IV. Power Spectrum Methodology and Results
• COMAP Early Science: III. CO Data Processing
• A multi-tracer empirically-driven approach to line-intensity mapping lightcones
• Exploration of 3D wavelet scattering transform coefficients for line-intensity mapping measurements
• The deconvolved distribution estimator: enhancing reionisation-era CO line-intensity mapping analyses with a cross-correlation analogue for one-point statistics
• Characteristic Functions for Cosmological Cross-Correlations
• COMAP Pathfinder -- Season 2 results I. Improved data selection and processing
• A Multi-messenger view of Cosmic Dawn: Conquering the Final Frontier
• Towards Accurate Modeling of Line-Intensity Mapping One-Point Statistics: Including Extended Profiles
• Towards Optimal Foreground Mitigation Strategies for Interferometric HI Intensity Mapping in the Low-Redshift Universe
• COMAP Pathfinder -- Season 2 results II. Updated constraints on the CO(1-0) power spectrum
• 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"
• Three-Dimensional Stacking as a Line Intensity Mapping Statistic
• Removal of interloper contamination to line-intensity maps using correlations with ancillary tracers of the large-scale structure