Volume 395 - 37th International Cosmic Ray Conference (ICRC2021) - CRI - Cosmic Ray Indirect
New Constraints on Cosmic Particle Populations at the Galactic Center using X-ray Observations of the Molecular Cloud Sagittarius B2
F. Rogers*, S. Zhang, K. Perez, M. Clavel and A. Taylor
Full text: pdf
Pre-published on: August 03, 2021
Published on:
Abstract
Located $\sim100$ pc from the dynamic center of the Milky Way, the molecular cloud Sagittarius B2 (Sgr B2) is the most massive such object in the Galactic Center region.
In X-rays, Sgr B2 shows a prominent neutral Fe K$\alpha$ line at 6.4 keV and continuum emission beyond 10 keV, indicating high-energy, non-thermal processes in the cloud.
The Sgr B2 complex is an X-ray reflection nebula whose total emissions have decreased since the year 2001 as it reprocesses what are likely one or more past energetic outbursts from the supermassive black hole Sagittarius A*. The X-ray reflection model explains the observed time-variability of the Fe K$\alpha$ and hard X-ray emissions, and it provides a window into the luminous history of our nearest supermassive black hole.
In light of evidence of elevated cosmic particle populations in the Galactic Center, recent interest has also focused on X-rays from Sgr B2 as a probe of low-energy (sub-GeV) cosmic particles.
In contrast to X-ray reflection, in this case we can assume that the X-ray flux contribution from ionization by low-energy cosmic particles is constant in time, such that upper limits on low-energy cosmic particle populations may be obtained using the lowest flux levels observed from the cloud.
Here, we present the most recent and correspondingly dimmest NuSTAR and XMM-Newton observations of Sgr B2, from 2018.
These reveal small-scale variations within lower density portions of the Sgr B complex, including brightening features, and enable the best upper limits on ionization of molecular clouds by low-energy cosmic particles in the inner $\sim100$ pc of the Galaxy.
DOI: https://doi.org/10.22323/1.395.0288
How to cite

Metadata are provided both in "article" format (very similar to INSPIRE) as this helps creating very compact bibliographies which can be beneficial to authors and readers, and in "proceeding" format which is more detailed and complete.

Open Access