Optical reconstruction of dust in the region of SNR RX J1713.7-3946 from
  astrometric data
  The origin of the radiation observed in the region of the supernova remnant
RX J1713.7-3946, one of the brightest TeV emitters, has been debated since its
discovery. The existence of atomic and molecular clouds in this object supports
the idea that part of the GeV gamma rays in this region originate from
proton-proton collisions. However, the observed column density of protons
derived from gas observations cannot explain the whole emission. Yet there
could be a fraction of protons contained in fainter structures that have note
been detected so far. Here we search for faint objects in the line of sight of
RX J1713.7-3946 using the principle of light extinction and the ESA/Gaia DR2
astrometric and photometric data. We reveal and locate with precision a number
of dust clouds and note that only one appears to be in the vicinity of RX
J1713.7-3946. We estimate the embedded mass to $M_{dust} = (7.0 \pm 0.6) \times
10^3 \, M_{\odot}$ which might be big enough to contain the missing protons.
Finally, using the fact that the supernova remnant is expected to be located in
a dusty environment and that there appears to be only one such structure in the
vicinity of RX J1713.7-3946, we set a very precise constrain to the supernova
remnant distance, at ($1.12 \pm 0.01$) kpc.
