SRG/eROSITA view of X-ray reflection in the Central Molecular Zone: a snapshot in September-October 2019

Abstract

X-ray reflection off dense molecular clouds in the Galactic Centre region has established itself as a powerful probe for the past activity record of the supermassive black hole Sgr A* on a timescale of a few hundred years. Detailed studies of the reflection signal from individual clouds allow us to estimate parameters of the brightest flare(s) and explore properties of the dense gas distribution inside and around them. On the other hand, wide area surveys covering the full Central Molecular Zone (CMZ) are crucial to spot brightening of the new clouds and long-term decay of the flux from the once bright ones. Here we present and discuss the data obtained by the SRG/eROSITA telescope in the course of its commissioning observations in late 2019 in regard to the X-ray reflection off CMZ clouds located to the East of Sgr A*. We measure the hard X-ray (4-8 keV) flux from the currently brightest (in reflected emission) molecular complex Sgr A and derive upper limits for other molecular complexes. We confirm that the Sgr A complex keeps being bright at the level of $4\times 10^{-13}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}\mathrm{arcmi}{\mathrm{n}}^{-2}$, making it an excellent candidate for the deep forthcoming high resolution imaging and polarimetric observations. We also discuss distinct features of the reflected emission from the clouds for which the primary illumination front has already passed away and the signal is dominated by multiply scattered radiation.

Accepted for publication in MNRAS; 9 pages, 6 figures, 1 table

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• X-ray polarization evidence for a 200 years-old flare of Sgr A${}^{\ast }$
• Study of the excess Fe XXV line emission in the central degrees of the Galactic centre using XMM-Newton data
• New Constraints on Cosmic Particle Populations at the Galactic Center using X-ray Observations of the Molecular Cloud Sagittarius B2
• 25 years of XMM-Newton observations of the Sgr A complex: 3D distribution and internal structure of the clouds
• North Polar Spur: gaseous plume(s) from star-forming regions at $\sim$3-5 kpc from Galactic Center?
• X-ray panorama of the SS433/W50 complex by SRG/eROSITA
• Perseus cluster in its X-ray entirety with SRG/eROSITA. Merger and Radio-Uroboroses
• High Energy Emission from the Galactic Center