Chandra Imaging of the X - ray Core of the Virgo Cluster

We report sub-arcsecond X-ray imaging spectroscopy of M87 and the core of the Virgo cluster with the Chandra X-ray Observatory. The X-ray morphology shows structure on arcsecond (∼ 100 pc) to ten arcminute (∼ 50 kpc) scales, the most prominent feature being an “arc” running from the east, across the central region of M87 and off to the southwest. A ridge in the radio map, ending in an “ear”-shaped structure, follows the arc to the east, and the radio emission appears to be wrapped around the arc to the southwest. Depressions in the X-ray surface brightness correspond to the inner radio lobes. There are also at least two approximately circular (centered near the nucleus) “edges” in the X-ray brightness distribution, the radii of which are similar to the nuclear distances of the inner radio lobes and intermediate radio ridges. We speculate that these discontinuities may be spherical pulses or “fronts” driven by the same jet activity as is responsible for the radio structure; such pulses are found in recent numerical simulations. All these results provide good evidence that the nuclear activity affects the intracluster medium. We compute temperature, pressure and cooling time maps, and confirm that the X-ray gas in the arc is cooler than, but may be slightly overpressured with respect to, the ambient cluster gas. The metal abundances of the gas in the arc are difficult to determine accurately, but the cooler gas is tentatively over-abundant in Si, S, and Fe relative to the ambient cluster gas, favoring a “buoyant plume” origin for the X-ray arc, in which ambient gas near the center is entrained and carried to larger distances. The gas temperature within the inner “front” (radius 45≃ 3.5 kpc) is cool (∼ 1.5 kev). This cool region is concentrated to the north of the nucleus and is strongly correlated with the Hα + [NII] emission-line distribution. Adjunct Astronomer, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 Royal Society University Research Fellow