Origin of the diffuse 4–8 keV emission in M 82

We present the first spatially resolved, X-ray spectroscopic study of 4-8 keV diffuse emission found in central part nearby starburst galaxy M82 on a few arcsecond scales. The new details that we see allow number important conclusions to be drawn nature hot gas and its origin as well feedback ISM. use archival data from Chandra with an exposure time 570 ks. Fexxv at 6.7 keV, expected metal-enriched gas, is enhanced only limited area close disc weak or almost absent over rest emission, resulting spatial variations EW <0.1 1.9 keV. This shows presence non-thermal due inverse Compton scattering FIR photons by radio emitting cosmic ray electrons. morphological resemblance between X-ray, radio, maps supports this concept. Our decomposition spectrum indicates ~70% luminosity originates emission. metal-rich kT~5 makes minor contribution continuum, but it accounts for majority observed line. appears emerge circumnuclear ring fill galactic chimneys identified mid-infrared voids. energetics argument suggests much supernova energy site has gone into creating transported halo. argue hot, rarefied environment produced strong results displacing brightest remnants which are instead reside GMC. find faint source counterpart, kinematic centre carefully examine possibility low-luminosity AGN ADAF phase.