We combined deep Chandra , ROSAT HRI , and XMM-Newton observations of M87 to study the impact of AGN outbursts on its gaseous atmosphere .
Many X-ray features appear to be a direct result of repetitive AGN outbursts .
In particular , the X-ray cavities around the jet and counter jet are likely due to the expansion of radio plasma , while rings of enhanced emission at 14 and 17 kpc are probably shock fronts associated with outbursts that began 1 - 2 \times 10 ^ { 7 } years ago .
The effects of these shocks are also seen in brightenings within the prominent X-ray arms .
On larger scales , \sim 50 kpc from the nucleus , depressions in the surface brightness may be remnants of earlier outbursts .
As suggested for the Perseus cluster ( Fabian et al .
) , our analysis of the energetics of the M87 outbursts argues that shocks may be the most significant channel for AGN energy input into the cooling flow atmospheres of galaxies , groups , and clusters .
For M87 , the mean power driving the shock outburst , 2.4 \times 10 ^ { 43 } ergs s ^ { -1 } , is three times greater than the radiative losses from the entire ‘ ‘ cooling flow ’ ’ .
Thus , even in the absence of other energy inputs , outbursts every 3 \times 10 ^ { 7 } years are sufficient to quench the flow .