The nearby elliptical galaxies NGC 4621 and NGC 4697 each host a supermassive black hole with M _ { \bullet } > 10 ^ { 8 } M _ { \odot } .
Analysis of archival Chandra data and new NRAO Very Large Array data shows that each galaxy contains a low-luminosity active galactic nucleus ( LLAGN ) , identified as a faint , hard X-ray source that is astrometrically coincident with a faint 8.5-GHz source .
The latter has a diameter less that 0.3″ ( 26 pc for NGC 4621 , 17 pc for NGC 4697 ) .
The black holes energizing these LLAGNs have Eddington ratios L ( 2 - 10 ~ { } keV ) / L ( Edd ) \sim 10 ^ { -9 } , placing them in the so-called quiescent regime .
The emission from these quiescent black holes is radio-loud , with log~ { } R _ { X } = log~ { } \nu L _ { \nu } ( 8.5 ~ { } GHz ) / L ( 2 - 10 ~ { } keV ) \sim - 2 , suggesting the presence of a radio outflow .
Also , application of the radio–X-ray–mass relation from Yuan & Cui for quiescent black holes predicts the observed radio luminosities \nu L _ { \nu } ( 8.5 ~ { } GHz ) to within a factor of a few .
Significantly , that relation invokes X-ray emission from the outflow rather than from an accretion flow .
The faint , but detectable , emission from these two massive black holes is therefore consistent with being outflow-dominated .
Observational tests of this finding are suggested .