Giant radio galaxies in the LOFAR Two-metre Sky Survey-I
  Giant radio galaxies (GRGs) are a subclass of radio galaxies which have grown
to megaparsec scales. GRGs are much rarer than normal sized radio galaxies (<
0.7 Mpc) and the reason for their gigantic sizes is still debated. Here, we
report the biggest sample of GRGs identified to date. These objects were found
in the LOFAR Two-metre Sky Survey (LoTSS) first data release images, which
cover a 424 square degrees region. Of the 239 GRGs found, 225 are new
discoveries. The GRGs in our sample have sizes ranging from 0.7 to 3.5 Mpc and
have redshifts (z) between 0.1 and 2.3. Seven GRGs have sizes above 2 Mpc and
one has a size of ~ 3.5 Mpc. The sample contains 40 GRGs hosted by
spectroscopically confirmed quasars. Here, we present the search techniques
employed and the resulting catalogue of the newly discovered large sample of
GRGs along with their radio properties. We, here also show for the first time
that the spectral index of GRGs is similar to that of normal sized radio
galaxies, indicating that most of the GRG population is not dead or is not like
remnant type radio galaxy. We find 20/239 GRGs in our sample are located at the
centres of clusters and present our analysis on their cluster environment and
radio morphology.
