Prospects for the polarimetric mapping of the Sgr A molecular cloud complex with IXPE

Abstract

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.

14 pages, 7 figures. Accepter for publication on Astronomy & Astrophysiscs

References in corpus (14)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• An XMM-Newton survey of broad iron lines in Seyfert galaxies
• Direct cosmological simulations of the growth of black holes and galaxies
• Detection of large-scale X-ray bubbles in the Milky Way halo
• Analyzing the Data from X-ray Polarimeters with Stokes Parameters
• Discovery of Variable Iron Fluorescence from Reflection Nebulae in the Galactic Center
• Not that long time ago in the nearest galaxy: 3D slice of molecular gas revealed by a 110 years old flare of Sgr A*
• An X-ray survey of the central molecular zone: variability of the Fe Ka emission line
• Prospects of 3D mapping of the Galactic Centre clouds with X-ray polarimetry
• Examining molecular clouds in the Galactic Centre region using X-ray reflection spectra simulations
• A Study of background for IXPE
• Reflection nebulae in the Galactic Center: the case for soft X-ray imaging polarimetry
• ESA Voyage 2050 white paper: A Polarized View of the Hot and Violent Universe

Cited by in corpus (3)

• X-ray polarization evidence for a 200 years-old flare of Sgr A${}^{\ast }$
• Testing particle acceleration models for BL LAC jets with the Imaging X-ray Polarimetry Explorer
• SRG/eROSITA view of X-ray reflection in the Central Molecular Zone: a snapshot in September-October 2019