Evidence for Molecular Gas in the Nucleus of M87 and Implications for the Fueling of Supermassive Black Holes

Supermassive black holes in the centers of giant elliptical galaxies are remarkably faint given their expected accretion rates. This motivates models of radiatively inefficient accretion, due to either thermal decoupling of ions from electrons, the generation of outflows or convective motions that inhibit accretion, or the settling of gas to a gravitationally unstable disk that forms stars in preference to feeding the black hole. A prediction of the latter model is the presence of cold molecular gas in a thin disk around the black hole. Here we report Submillimeter Array observations of the nucleus of the giant elliptical galaxy M87 and the tentative detection of CO(J=2–1) line emission at the position and velocity of the black hole. The implied molecular gas mass is 4.3± 1.2× 10M⊙, in agreement with the predictions of Tan & Blackman (2005). We also detect 1.3 mm continuum emission from the nucleus and several knots in the jet, including one that has been undergoing a flare.