Large-scale 3D mapping of the intergalactic medium using the Lyman Alpha
  Forest
  Maps of the large-scale structure of the Universe at redshifts 2-4 can be
made with the Lyman-alpha forest which are complementary to low redshift galaxy
surveys. We apply the Wiener interpolation method of Caucci et al. to construct
three-dimensional maps from sets of Lyman-alpha forest spectra taken from
cosmological hydrodynamic simulations. We mimic some current and future quasar
redshift surveys (BOSS, eBOSS and MS-DESI) by choosing similar sightline
densities. We use these appropriate subsets of the Lyman-alpha absorption
sightlines to reconstruct the full three dimensional Lyman-alpha flux field and
perform comparisons between the true and the reconstructed fields. We study
global statistical properties of the intergalactic medium (IGM) maps with
auto-correlation and cross-correlation analysis, slice plots, local peaks and
point by point scatter. We find that both the density field and the statistical
proper- ties of the IGM are recovered well enough that the resulting IGM maps
can be meaningfully considered to represent large-scale maps of the Universe in
agreement with Caucci et al., on larger scales and for sparser sightlines than
had been tested previously. Quantitatively, for sightline parameters comparable
to current and near future surveys the correlation coefficient between true and
reconstructed fields is r > 0.9 on scales > 30 h^-1 Mpc. The properties of the
maps are relatively insensitive to the precise form of the covariance matrix
used. The final BOSS quasar Lyman-alpha forest sample will allow maps to be
made with a resolution of ~ 30 h^-1 Mpc over a volume of ~ 15 h^-3 Gpc^3
between redshifts 1.9 and 2.3.
