SIMBAD references

We compare a very deep X-ray image of M87, at the center of the Virgo Cluster, to high-quality optical images of the low-excitation emission-line gas in the same region. There are striking coincidences of detail between the two. We explore the possibility that this represents a thermal interaction between hot gas at 10⁷ K and warm gas at 10⁴ K. We find that two temperatures are present in the X-ray gas, with the lower more prevalent in the vicinity of the optical filaments. Electron conduction from the hot phase to the cooler one provides a quantitatively acceptable energy source for the optical filaments, and we show additionally that it can do so for the brightest X-ray cluster, Perseus. If operative, conduction in the presence of gas-rich galaxy mergers may explain the presence of ``cool cores'' in clusters of galaxies.