The Galactic Faraday rotation sky 2020
  This work gives an update to existing reconstructions of the Galactic Faraday
rotation sky by processing almost all Faraday rotation data sets available at
the end of the year 2020. Observations of extra-Galactic sources in recent
years have, among other regions, further illuminated the previously
under-constrained southern celestial sky, as well as parts of the inner disc of
the Milky Way. This has culminated in an all-sky data set of 55,190 data
points, which is a significant expansion on the 41,330 used in previous works,
hence making an updated separation of the Galactic component a promising
venture. The increased source density allows us to present our results in a
resolution of about $1.3\cdot 10^{-2}\, \mathrm{deg}^2$
($46.8\,\mathrm{arcmin}^2$), which is a twofold increase compared to previous
works. As for previous Faraday rotation sky reconstructions, this work is based
on information field theory, a Bayesian inference scheme for field-like
quantities which handles noisy and incomplete data. In contrast to previous
reconstructions, we find a significantly thinner and pronounced Galactic disc
with small-scale structures exceeding values of several thousand
$\mathrm{rad}\,\mathrm{m}^{-2}$. The improvements can mainly be attributed to
the new catalog of Faraday data, but are also supported by advances in
correlation structure modeling within numerical information field theory. We
furthermore give a detailed discussion on statistical properties of the Faraday
rotation sky and investigate correlations to other data sets.
