Lyman-alpha forest tomography and cross-correlation with cosmic voids
  The Lyman-alpha forest is a unique probe of large-scale matter density
fluctuations at high redshift (z > 2). It is possible to obtain 3D maps of the
matter distribution from Lyman-alpha data, using tomographic reconstruction
methods. Here, we present the largest tomographic map of matter fluctuations at
z > 2, over the Gpc^3 volume covered by Lyman-alpha forest from SDSS-IV quasar
spectra in the Stripe 82 field. We present a catalog of high-redshift voids
constructed from this map. The measurement of the cross-correlation between
these voids and the Lyman-alpha forest provides the first observation of the
matter velocity flow around voids, through the RSD effect, at such high
redshift. The data is in good agreement with simulations and is well adjusted
with a linear, Kaiser velocity model.
