ASCA observations of non‐thermal emissions from groups of galaxies

ASCA detected hard X-ray emission associated with several groups of galaxies. Analysis of HCG62 data, whose data quality is the best of all, indicates that hard X-ray emission is extended over groups. The luminosity of hard emission is typically 1041–42 erg/s. The possible emission mechanism is non-thermal bremsstrahlung by sub-relativistic particles or inverse compton scattering of CMB photons by relativistic electrons. Whichever it is, leading results will be interesting for studies of particle acceleration in the clusters of galaxies.