Spatial diffusion of X-ray emission lines in the M87 cooling flow; evidence for absorption

Recent XMM-Newton observations of the cooling flow in M87 indicate sharply decreasing oxygen, iron, and silicon abundances within similar to5 kpc of t he galactic center. This result is unexpected since stellar mass loss and T ype Ia supernovae are expected to produce pronounced central abundance maxi ma for all three elements. However, it has been suggested that many of the strong X-ray lines are optically thick and diffuse to larger radii in the c ooling flow before escaping, falsifying the central abundances. We verify w ith radiation transfer calculations that this effect does indeed occur in t he M87 cooling flow but that it is insufficient to account for the M87 obse rvations. We suggest that some source of continuous opacity is required to reduce the central X-ray line emission, perhaps by warm gas at T similar to 10(5) -10(6) K. The radial surface brightness profiles of X-ray resonance lines are also sensitive to turbulence in cooling flows, which reduces the line center optical depths considerably. Turbulence may provide sufficient energy to continuously heat the warm absorbing gas.