  After the jets have switched off, radio galaxies undergo a fading phase which
is often named the dying phase. The luminosity evolution of the remnant plasma
during this period is still poorly constrained because of the paucity of
objects detected. Using the new 150-MHz deep LOFAR observations of the
well-known extragalactic field the Lockman Hole, we performed a systematic
search of dying radio sources aiming to provide good statistics on their
detection and properties. To avoid selection biases towards any specific class
of dying sources we used both morphological and spectral selection criteria. To
do this we combined the LOFAR data with publicly available surveys at other
frequencies as well as dedicated deep observations. Our preliminary results,
show that the fraction of candidate dying radio sources is < 6-8% of the entire
radio source population and is dominated by steep spectrum sources. By
comparing these observational results with statistical modelling of the radio
sky population we will be able to constrain the main mechanisms contributing to
the dying radio galaxy luminosity evolution.
