Probing the Galactic center with X-ray polarimetry
  The Galactic center (GC) holds the closest-to-Earth supermassive black hole
(SMBH), which makes it the best laboratory to study the close environment of
extremely massive compact objects. Polarimetry is sensitive to geometry of the
source, which makes it a particularly suitable technique to probe the medium
surrounding the GC SMBH. The detection of hard X-ray spectra and prominent iron
K$\alpha$ fluorescence features coincident with localized gas clouds (e.g.
Sgr~B2, Sgr~C) is known for nearly twenty years now and is commonly associated
with a past outburst of the SMBH whose radiation is reprocessing onto the
so-called "reflection nebulae". Since scattering leads to polarization, the
re-emitted signal from the giant molecular clouds in the first 100~pc of the GC
is expected to be polarized. X-ray polarization measurement is thus
particularly adapted to probe the origin of the diffuse X-ray emission from the
GC reflection nebulae and reveal the past activity of the central SMBH. In this
research note, we summarize the results from past and current polarimetric
simulations in order to show how a future X-ray polarimeter equipped with
imaging detectors could improve our understanding of high-energy astrophysics.
