Abstract
It has been realised only recently that TeV emission from blazars can
significantly heat the intergalactic medium (IGM) by pair-producing high-energy
electrons and positrons, which in turn excite vigorous plasma instabilities,
leading to a local dissipation of the pairs' kinetic energy. In this work, we
use cosmological hydrodynamical simulations to model the impact of this induced
blazar heating on the Lyman-alpha forest at intermediate redshifts (z~2-3). We
find that blazar heating produces an inverted equation-of-state in the IGM and
naturally resolves many of the problems present in previous simulations of the
forest that included photoionisation heating alone. In particular, our
simulation results simultaneously reproduce the observed effective optical
depth and temperature as a function of redshift, the observed probability
distribution functions (PDFs) of the transmitted flux, and the observed flux
power spectra, over the full redshift range 2<z<3 analysed here. Additionally,
by deblending the absorption features of Lyman-alpha spectra into a sum of
thermally broadened individual lines, we find superb agreement with the
observed lower cutoff of the line-width distribution and abundances of neutral
hydrogen column densities per unit redshift. Using the most recent constraints
on the cosmic ultraviolet (UV) background, this excellent agreement with
observations is obtained without re-scaling the amplitude of the UV background;
a procedure that was routinely used in the past to match the observed level of
transmitted flux. This concordance between Lyman-alpha data and simulation
results, which are based on the most recent cosmological parameters, also
suggests that the inclusion of blazar heating alleviates previous tensions on
constraints for sigma_8 derived from Lyman-alpha measurements and other
cosmological data. abridged
Description
[1107.3837] The Lyman-alpha forest in a blazar-heated Universe
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