skip to main content

SciTech ConnectSciTech Connect

Title: Lyα heating of inhomogeneous high-redshift intergalactic medium

The intergalactic medium (IGM) prior to the epoch of reionization consists mostly of neutral hydrogen gas. Lyman-α (Lyα) photons produced by early stars resonantly scatter off hydrogen atoms, causing energy exchange between the radiation field and the gas. This interaction results in moderate heating of the gas due to the recoil of the atoms upon scattering, which is of great interest for future studies of the pre-reionization IGM in the H I 21 cm line. We investigate the effect of this Lyα heating in the IGM with linear density, temperature, and velocity perturbations. Perturbations smaller than the diffusion length of photons could be damped due to heat conduction by Lyα photons. The scale at which damping occurs and the strength of this effect depend on various properties of the gas, the flux of Lyα photons, and the way in which photon frequencies are redistributed upon scattering. To find the relevant length scale and the extent to which Lyα heating affects perturbations, we calculate the gas heating rates by numerically solving linearized Boltzmann equations in which scattering is treated by the Fokker-Planck approximation. We find that (1) perturbations add a small correction to the gas heating rate, and (2) the dampingmore » of temperature perturbations occurs at scales with comoving wavenumber k ≳ 10{sup 4} Mpc{sup –1}, which are much smaller than the Jeans scale and thus unlikely to substantially affect the observed 21 cm signal.« less
Authors:
;  [1]
  1. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22348423
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; ATOMS; BOLTZMANN EQUATION; DENSITY; DIFFUSION LENGTH; DISTURBANCES; FOKKER-PLANCK EQUATION; GALAXIES; HEATING RATE; INTERACTIONS; INTERGALACTIC SPACE; PERTURBATION THEORY; PHOTONS; RADIANT HEAT TRANSFER; RECOILS; RED SHIFT; SCATTERING; STARS; THERMAL CONDUCTION; UNIVERSE