15-20 March 2020
Europe/Berlin timezone

X-ray to gamma-ray virial shock signal from the Coma cluster

Not scheduled




Following evidence for an east--west elongated virial ring around the Coma galaxy cluster in a $\sim220$ GeV VERITAS mosaic, we search for corresponding signatures in $>$GeV $\gamma$-rays from Fermi-LAT, and in soft, $\sim0.1$ keV X-rays from ROSAT.
For the ring elongation and orientation inferred from VERITAS, we find a nominal $3.4\sigma$ LAT excess, and the expected signature ($>5\sigma$) in ROSAT bands R1 and R1+R2.
The significances of both LAT and ROSAT signals are maximal near the VERITAS ring parameters.
The intensities of the ROSAT, Fermi, and VERITAS signals are consistent with the virial shock depositing $\sim0.3\%$ (with an uncertainty factor of $\sim3$) of its energy over a Hubble time in a nearly flat, $p\equiv - d\ln N_e/d\ln E\simeq 2.0$--$2.2$ spectrum of cosmic-ray electrons.
The sharp radial profiles of the LAT and ROSAT signals suggest preferential accretion in the plane of the sky, as indicated by the distribution of neighboring large-scale structure.
The X-ray signal gauges the compression of cosmic-rays as they are advected deeper into the cluster. Using eRosita, which has better resolution and sensitivity than ROSAT can help us to better constrain the measurements in Coma and to detect more virial rings in the X-rays in other clusters.

Primary authors

Ido Reiss (Ben Gurion University) Uri Keshet (Ben-Gurion University of the Negev)

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