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arXiv · 2407.03060

Effect of Ly$α$ Radiative Transfer on Intensity Mapping Power Spectra

Maja Lujan Niemeyer
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Abstract

Clustering of Ly$α$-emitting galaxies (LAEs) and Ly$α$ line intensity mapping (LIM) are useful probes of cosmology. However, Ly$α$ radiative transfer (RT) effects, such as absorption, line shift, and line broadening, and their dependence on the large-scale density and velocity fields can modify the measured LAE clustering and LIM statistics. We explore the effects of RT on the Ly$α$ LIM power spectrum in two ways: using an analytic description based on linear approximations, and using lognormal mocks. The qualitative effects of intergalactic Ly$α$ absorption on the LIM auto- and cross-power spectrum include a scale-dependent, reduced effective bias, reduced mean intensity, and modified redshift-space distortions. The linear absorption model does not describe the results of the lognormal simulations well. The random line shift suppresses the redshift-space power spectrum similar to the Fingers-of-God effect. In cross-correlation of LAEs or Ly$α$ intensity with a non-Ly$α$ tracer, the Ly$α$ line shift leads to a phase shift of the complex power spectrum, i.e. a cosine damping of the real part. We study the impact of Ly$α$ RT effects on the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) LAE and LIM power spectra using lognormal mocks. We find that even small amounts of IGM absorption will significantly change the measured LAE auto-power spectrum. The LAE-intensity cross-power spectrum stays within the measurement uncertainty. Therefore, HETDEX will be able to constrain Ly$α$ RT effects.

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Maja Lujan Niemeyer. 2025-02-03. Effect of Ly$α$ Radiative Transfer on Intensity Mapping Power Spectra. https://arxiv.org/abs/2407.03060

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