Lyman-alpha Emission From Cosmic Structure I: Fluorescence
  We present predictions for the fluorescent Lyman-alpha emission signature
arising from photoionized, optically thick structures in Smoothed Particle
Hydrodynamic (SPH) cosmological simulations of a Lambda-CDM universe using a
Monte Carlo Lyman-alpha radiative transfer code. We calculate the expected
Lyman-alpha image and 2-dimensional spectra for gas exposed to a uniform
ultraviolet ionizing background as well as gas exposed additionally to the
photoionizing radiation from a local quasar, after correcting for the
self-shielding of hydrogen. As a test of our numerical methods and for
application to current observations, we examine simplified analytic structures
that are uniformly or anisotropically illuminated. We compare these results
with recent observations. We discuss future observing campaigns on large
telescopes and realistic strategies for detecting fluorescence owing to the
ambient metagalactic ionization and in regions close to bright quasars. While
it will take hundreds of hours on the current generation of telescopes to
detect fluorescence caused by the ultraviolet background (UVB) alone, our
calculations suggest that of order ten sources of quasar-induced fluorescent
Lyman-alpha emission should be detectable after a 10 hour exposure in a 10
arcmin^2 field around a bright quasar. These observations will help probe the
physical conditions in the densest regions of the intergalactic medium as well
as the temporal light curves and isotropy of quasar radiation.
