Millimeter Radio Continuum Emissions as the Activity of Super Massive
  Black Holes in Nearby Early-Type Galaxies and Low-Luminosity Active Galactic
  Nuclei
  We conducted millimeter continuum observations for samples of nearby
early-type galaxies (21 sources) and nearby low-luminosity active galactic
nuclei (LLAGN; 16 sources) at 100 GHz (3 mm) using the Nobeyama Millimeter
Array (NMA). In addition, we performed quasi-simultaneous observations at 150
GHz (2 mm) and 100 GHz for five LLAGNs. Compact nuclear emissions showing flat
or inverted spectra at centimeter-to-millimeter wavelengths were found in many
LLAGNs and several early-type galaxies. Moreover, significant flux variability
was detected in three LLAGNs. These radio properties are similar to Sgr A*. The
observed radio luminosities are consistent with the fundamental plane of black
hole activity that has suggested on the basis of samples with black hole masses
ranging from 10 to 10^10 M_sun. This implies nuclear jets powered by
radiatively inefficient accretion flows onto black holes.
