Studying the late evolution of a radio-loud AGN in a galaxy group with
  LOFAR
  Feedback by radio-loud active galactic nuclei (AGN) in galaxy groups is not
fully understood. Open questions include the duty cycle of the AGN, the spatial
extent of the radio lobes, the effect they have on the intragroup medium, and
the fate of the cosmic rays. We present the discovery of a 650 kpc-radio galaxy
embedded in steep diffuse emission at $z = 0.18793 \pm 5 \times 10^{-5}$
located at the center of the galaxy group MaxBCG J199.31832+51.72503 using an
observation from the LOFAR Two-meter Sky Survey (LoTSS) at the central
frequency of 144 MHz. Subsequently, we performed a GMRT observation at the
central frequency of 607 MHz to study the spectral properties of the source.
The observations reveal a radio galaxy with a total radio power $P_{\rm tot,
1.4} \sim 2.1 \times 10^{24}$ W Hz$^{-1}$, exhibiting two asymmetrical jets and
lobes. The derived spectral index map shows a steepening toward the inner
regions and a steep-spectrum core region. We model the integrated radio
spectrum, providing two possible interpretations: the radio source is evolved
but still active or it is just at the end of its active phase. Finally, in the
same field of view we have discovered Mpc-sized emission surrounding a close
pair of AGN located at a redshift $z = 0.0587 \pm 2 \times 10^{-4}$ (SDSS
J131544.56+521213.2 and SDSS J131543.99+521055.7) which could be a radio
remnant source.
