The New Class of FR0 Radio Galaxies

Abstract

Recently, there are evidences that an emerging population of compact radio galaxies which lack of extended radio emission might be crucial in the comprehension of the radio-loud AGN population in the local Universe. In a pilot JVLA project, we observe a small but representative subsample of this population. The radio maps reveal compact unresolved or slightly resolved radio structures on a scale of 1-3 kpc. We find that these radio-loud AGN live in red massive early-type galaxies, with large black hole masses (~10^{8} solar mass), and spectroscopically classified as Low Excitation Galaxies, all characteristics typical of FRI radio galaxies which they also share the same (optical and X-ray) nuclear luminosity with. However, they are more core dominated (by a factor of ~30) than FRIs and show a clear deficit of extended radio emission. We call these sources 'FR0' to emphasize their lack of prominent extended radio emission. The emerging FR0 population appears to be the dominant radio class of the local Universe (~10 times more abundant than local FRIs). Considering their properties we speculate their possible origins and the possible cosmological scenarios they imply. </p