Lyman-α polarization intensity mapping
- Creators
- Mas-Ribas, Lluís
- Chang, Tzu-Ching
Abstract
We present a formalism that incorporates hydrogen Lyman-alpha (Lyα) polarization arising from the scattering of radiation in galaxy halos into the intensity mapping approach. Using the halo model, and Lyα emission profiles based on simulations and observations, we calculate auto and cross power spectra at redshifts 3 ≤ z ≤ 13 for the Lyα total intensity, I, polarized intensity, P, degree of polarization, Π=P/I, and two new quantities, the astrophysical E and B modes of Lyα polarization. The one-halo terms of the Π power spectra show a turnover that signals the average extent of the polarization signal, and thus the extent of the scattering medium. The position of this feature depends on redshift, as well as on the specific emission profile shape and extent, in our formalism. Therefore, the comparison of various Lyα polarization quantities and redshifts can break degeneracies between competing effects, and it can reveal the true shape of the emission profiles, which, in turn, are associated to the physical properties of the cool gas in galaxy halos. Furthermore, measurements of Lyα E and B modes may be used as probes of galaxy evolution, because they are related to the average degree of anisotropy in the emission and in the halo gas distribution across redshifts. The detection of the polarization signal at z∼3–5 requires improvements in the sensitivity of current ground-based experiments by a factor of ∼10, and of ∼100 for space-based instruments targeting the redshifts z∼9–10, the exact values depending on the specific redshift and experiment. Interloper contamination in polarization is expected to be small, because the interlopers need to also be polarized. Overall, Lyα polarization boosts the amount of physical information retrievable on galaxies and their surroundings, most of it not achievable with total emission alone.
Additional Information
© 2020 American Physical Society. Received 10 February 2020; accepted 6 April 2020; published 29 April 2020. We are grateful to Agnès Ferté for an inspiring discussion that motivated the idea of considering polarization in intensity mapping experiments. We are indebted to Chris Hirata and Siavash Yasini, who greatly contributed to the derivation of the Lyman-alpha E and B mode formalism, and to Bryan Steinbach and Emmanuel Schaan for noting the nature of the shot-noise terms. We thank our colleagues Peter Laursen, Phil Korngut, Jason Sun, Phil Berger, Marta Silva, Matt Johnson, Chen Heinrich, Isabel Swafford, Marlee Smith, Adam Lidz, Fred Davies, Jae Hwan Kang, Jordi Miralda Escudé, and others for comments and discussions during this project. We are also thankful to Bin Yue and Maxime Trebitsch for noting the effect of weak lensing on the polarization signal. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).Attached Files
Published - PhysRevD.101.083032.pdf
Accepted Version - 2002.04107.pdf
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Additional details
- Eprint ID
- 102903
- Resolver ID
- CaltechAUTHORS:20200429-104550904
- NASA/JPL/Caltech
- 80NM0018D0004
- NASA
- Created
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2020-04-29Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field