Lenses in the forest: cross-correlation of the Lyman-alpha flux with CMB lensing

Abstract

We present a theoretical estimate for a new observable: the cross-correlation between the Lyman-alpha flux fluctuations in quasar (QSO) spectra and the convergence of the cosmic microwave background (CMB) as measured along the same line-of-sight. As a first step toward the assessment of its detectability, we estimate the signal-to-noise ratio using linear theory. Although the signal-to-noise is small for a single line-of-sight and peaks at somewhat smaller redshifts than those probed by the Lyman-alpha forest, we estimate a total signal-to-noise of 9 for cross-correlating QSO spectra of SDSS-III with Planck and of 20 for cross-correlating with a future polarization based CMB experiment. The detection of this effect would be a direct measure of the neutral hydrogen-matter cross-correlation and could provide important information on the growth of structures at large scales in a redshift range which is still poorly probed by observations.

5 pages, 4 figures, matches published version

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Cited by in corpus (5)

• ACTPol: A polarization-sensitive receiver for the Atacama Cosmology Telescope
• The High Redshift Integrated Sachs-Wolfe Effect
• First Detection of Cosmic Microwave Background Lensing and Lyman-α Forest Bispectrum
• Constraining dark energy using the cross correlations of weak lensing with post-reionization probes of neutral hydrogen
• Probing Quintessence using BAO imprint on the cross-correlation of weak lensing and post-reionization HI 21 cm signal