Lyman-αpolarization intensity mapping

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 calcualte 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.

The thesan project: predictions for multitracer line intensity mapping in the epoch of reionization

“…Beyond this, the prominent Ly α transition (2-1) of neutral hydrogen is an exceptionally promising target for upcoming intensity mapping experiments like SPHEREx and CDIM (e.g. Visbal & McQuinn 2018 ;Mas-Ribas & Chang 2020 ). Part of the utility of Ly α stems from the additional physics of resonant absorption, which ef fecti v ely remo v es Ly α photons out of the line of sight to be lost to the diffuse cosmic optical and infrared backgrounds (Gunn & Peterson 1965 ).…”

The THESAN project: predictions for multi-tracer line intensity mapping in the Epoch of Reionization

“…Beyond this, the prominent Ly 𝛼 transition (2-1) of neutral hydrogen is an exceptionally promising target for upcoming intensity mapping experiments like SPHEREx and CDIM (e.g. Visbal & Mc-Quinn 2018;Mas-Ribas & Chang 2020). Part of the utility of Ly 𝛼 stems from the additional physics of resonant absorption, which effectively removes Ly 𝛼 photons out of the line of sight to be lost to the diffuse cosmic optical and infrared backgrounds (Gunn & Peterson 1965).…”

Cosmological Constraints on the Global Star Formation Law of Galaxies: Insights from Baryon Acoustic Oscillation Intensity Mapping

“…Historically, large-scale fluctuations of line intensity fields have been mainly considered for cosmological applications, such as probing alternative dark matter models, dark energy, gravitational lensing, neutrino properties, and the primordial non-Gaussianity (e.g., Sitwell et al 2014;Karkare & Bird 2018;Bernal et al 2019;Liu & Breysse 2021;Chung 2022;Maniyar et al 2022;Moradinezhad Dizgah et al 2022). The majority of astrophysical explorations of LIM have been focusing on small, nonlinear scales, where astrophysical processes of galaxy evolution are manifested through their effects on the one-halo or shot-noise components of the LIM power spectrum (e.g., Wolz et al 2017;Breysse & Alexandroff 2019;Mas-Ribas & Chang 2020;Schaan & White 2021). Therefore, it is interesting to extend the scope of astrophysical information from LIM to the linear regime by measuring baryon fraction fluctuations with BAO intensity mapping.…”