Detection of virial shocks in Fermi LAT galaxy clusters

by Ido Reiss

at Astrophysics and Cosmology Seminar

Wed, 17 Jan 2018, 11:15
Physics building (#54) room 207

Abstract

Galaxy clusters are thought to grow by accreting mass through large scale strong yet elusive virial shocks These collisionless shocks are thought to accelerate relativistic electrons generating a spectrally flat leptonic virial ring However with the exception of a VERITAS signal from the Coma cluster attempts to detect virial rings have all failed By stacking and rescaling Fermi LAT data at 1 100GeV for the 112 most massive high latitude extended clusters we identify at the 5 9 sigma confidence level a bright spectrally flat gamma ray ring at the expected radius This indicates that 0 6 with an uncertainty factor 2 of the thermal energy is deposited in relativistic electrons over a Hubble time This detection is confirmed using two multi messenger analyses of individual clusters: 1 A combined VERITAS 220GeV LAT and ROSAT R1 0 2keV elliptical signal in Coma 2 Planck SZ pressure near the virial radius coincident with a LAT gamma ray excess in Coma A2319 and A2142 This results validate the shock paradigm calibrate its parameters and indicate that such shocks significantly contribute to the diffuse extragalactic gamma ray and radio backgrounds

Created on 07-01-2018 by Bar Lev, Yevgeny (ybarlev)
Updaded on 07-01-2018 by Bar Lev, Yevgeny (ybarlev)