Cosmic evolution of low-excitation radio galaxies in the LOFAR Two-meter
  Sky Survey Deep Fields
  Feedback from low-excitation radio galaxies (LERGs) plays a key role in the
lifecycle of massive galaxies in the local Universe; their evolution, and the
impact of these active galactic nuclei on early galaxy evolution, however,
remain poorly understood. We use a sample of 10481 LERGs from the first data
release of the LOFAR Two-meter Sky Survey Deep Fields, covering $\sim$ 25
deg$^2$, to present the first measurement of the evolution of the radio
luminosity function (LF) of LERGs out to $z\sim2.5$; this shows relatively mild
evolution. We split the LERGs into those hosted by quiescent and star-forming
galaxies, finding a new dominant population of LERGs hosted by star-forming
galaxies at high redshifts. The incidence of LERGs in quiescent galaxies shows
a steep dependence on stellar-mass out to $z \sim1.5$, consistent with local
Universe measurements of accretion occurring from cooling of hot gas haloes.
The quiescent-LERGs dominate the LFs at $z<1$, showing a strong decline in
space density with redshift, tracing that of the available host galaxies, while
there is an increase in the characteristic luminosity. The star-forming LERG LF
increases with redshift, such that this population dominates the space
densities at most radio-luminosities by $z \sim 1$. The incidence of LERGs in
star-forming galaxies shows a much weaker stellar-mass dependence, and
increases with redshift, suggesting a different fuelling mechanism compared to
their quiescent counterparts, potentially associated with the cold gas supply
present in the star-forming galaxies.
