The peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?
  Using observations obtained with the LOw Fequency ARray (LOFAR), the
Westerbork Synthesis Radio Telescope (WSRT) and archival Very Large Array (VLA)
data, we have traced the radio emission to large scales in the complex source
4C 35.06 located in the core of the galaxy cluster Abell 407. At higher spatial
resolution (~4"), the source was known to have two inner radio lobes spanning
31 kpc and a diffuse, low-brightness extension running parallel to them, offset
by about 11 kpc (in projection).
  At 62 MHz, we detect the radio emission of this structure extending out to
210 kpc. At 1.4 GHz and intermediate spatial resolution (~30"), the structure
appears to have a helical morphology.
  We have derived the characteristics of the radio spectral index across the
source. We show that the source morphology is most likely the result of at
least two episodes of AGN activity separated by a dormant period of around 35
Myr.
  The AGN is hosted by one of the galaxies located in the cluster core of Abell
407. We propose that it is intermittently active as it moves in the dense
environment in the cluster core. Using LOFAR, we can trace the relic plasma
from that episode of activity out to greater distances from the core than ever
before.
  Using the the WSRT, we detect HI in absorption against the center of the
radio source. The absorption profile is relatively broad (FWHM of 288 km/s),
similar to what is found in other clusters.
  Understanding the duty cycle of the radio emission as well as the triggering
mechanism for starting (or restarting) the radio-loud activity can provide
important constraints to quantify the impact of AGN feedback on galaxy
evolution. The study of these mechanisms at low frequencies using morphological
and spectral information promises to bring new important insights in this
field.
