VLA Radio Study of a Sample of Nearby X-ray and Optically Bright
  Early-Type Galaxies
  Many massive early-type galaxies host central radio sources and hot X-ray
atmospheres indicating the presence of radio-mechanical active galactic nucleus
(AGN) feedback. The duty cycle and detailed physics of the radio-mode AGN
feedback is still a matter of debate. To address these questions, we present
1-2 GHz Karl G. Jansky Very Large Array (VLA) radio observations of a sample of
the 42 nearest optically and X-ray brightest early-type galaxies. We detect
radio emission in 41/42 galaxies. However, the galaxy without a radio source,
NGC 499, has recently been detected at lower frequencies by the Low-Frequency
Array (LOFAR). Furthermore, 27/42 galaxies in our sample host extended radio
structures and 34/42 sources show environmental interactions in the form of
X-ray cavities. We find a significant correlation between the radio flux
density and the largest linear size of the radio emission and between the radio
power and the luminosity of the central X-ray point-source. The central radio
spectral indices of the galaxies span a wide range of values, with the majority
of the systems having steep spectra and the rest flat spectra. These results
are consistent with AGN activity, where the central radio sources are mostly
switched on, thus the duty cycle is very high. 7/14 galaxies with point-like
radio emission (Fanaroff-Riley Class 0; FR 0) also show X-ray cavities
indicating that, despite the lack of extended radio structures at 1-2 GHz,
these AGN do launch jets capable of inflating lobes and cavities.
