Prospects for the polarimetric mapping of the Sgr A molecular cloud
  complex with IXPE
  The X-ray polarization degree of the molecular clouds that surround Sgr A* is
expected to be greatly lowered because the polarized reflection emission is
mixed with the unpolarized thermal emission that pervades the Galactic center
region. Hence, this will be a challenging observation for the upcoming Imaging
X-ray Polarimeter Explorer (IXPE). We aim to determine the detectability of
four molecular clouds (MC) of the Sgr A complex (MC2, Bridge B2, Bridge E, and
G0.11-0.11) in a realistic IXPE pointing of the Sgr A field of view. We assess
the Minimum Detectable Polarization (MDP) increase when a MC is off axis. We
provide two different strategies to reconstruct the intrinsic cloud
polarization once the data will be available. We use the Monte Carlo tool
ixpeobssim to simulate IXPE observations of the Sgr A MC complex. We use
Chandra maps and spectra to model the diffuse emission in the Galactic center
region along with a realistic model of the instrumental and diffuse background.
We create synthetic polarization products of the unpolarized emission. We
combine them with a test dataset from a simulation of a 2 Ms long IXPE
observation to retrieve the intrinsic polarization degree of the MCs. We find
that for the MC considered here, the MDP increases by 1-15% with respect to the
case in which a cloud is observed on-axis. We successfully retrieve the
intrinsic polarization degree in the 4.0-8.0 keV band and line-of-sight
distance of one of them taken as an example, G0.11-0.11, by correcting the
observed (i.e., for a 2 Ms-long simulation) polarization degree map using
either a synthetic dilution map or a Stokes intensity map of the unpolarized
emission. With both methods, the position of the cloud along the line-of-sight
is derived from the reconstructed polarization degree with an uncertainty of 7
and 4 pc, respectively.
