A population of galaxy-scale jets discovered using LOFAR
  The effects of feedback from high luminosity radio-loud AGN have been
extensively discussed in the literature, but feedback from low-luminosity
radio-loud AGN is less well understood. The advent of high sensitivity, high
angular resolution, large field of view telescopes such as LOFAR is now
allowing wide-area studies of such faint sources for the first time. Using the
first data release of the LOFAR Two Metre Sky Survey (LoTSS) we report on our
discovery of a population of 195 radio galaxies with 150 MHz luminosities
between $3\times10^{22}$ and $1.5\times10^{25}\text{ W Hz}^{-1}$ and total
radio emission no larger than 80 kpc. These objects, which we term galaxy-scale
jets (GSJ), are small enough to be directly influencing the evolution of the
host on galaxy scales. We report upon the typical host properties of our
sample, finding that 9 per cent are hosted by spirals with the remainder being
hosted by elliptical galaxies. Two of the spiral-hosted GSJ are highly unusual
with low radio luminosities and FRII-like morphology. The host properties of
our GSJ show that they are ordinary AGN observed at a stage in their life
shortly after the radio emission has expanded beyond the central regions of the
host. Based on our estimates, we find that about half of our GSJ have internal
radio lobe energy within an order of magnitude of the ISM energy so that, even
ignoring any possible shocks, GSJ are energetically capable of affecting the
evolution of the host. The current sample of GSJ will grow in size with future
releases of LoTSS and can also form the basis for further studies of feedback
from low-luminosity radio sources.
