uGMRT detection of cluster radio emission in low-mass Planck~SZ clusters
  Low-mass ($M_{\rm{500}}<5\times10^{14}{\rm{M_\odot}}$) galaxy clusters have
been largely unexplored in radio observations, due to the inadequate
sensitivity of existing telescopes. However, the upgraded GMRT (uGMRT) and the
Low Frequency ARray (LoFAR), with unprecedented sensitivity at low frequencies,
have paved the way to closely study less massive clusters than before. We have
started the first large-scale programme to systematically search for diffuse
radio emission from low-mass galaxy clusters, chosen from the Planck
Sunyaev-Zel'dovich cluster catalogue. We report here the detection of diffuse
radio emission from four of the 12 objects in our sample, shortlisted from the
inspection of the LoFAR Two Meter Sky Survey (LoTSS-I), followed up by uGMRT
Band 3 deep observations. The clusters PSZ2~G089 (Abell~1904) and PSZ2~G111
(Abell~1697) are detected with relic-like emission, while PSZ2~G106 is found to
have an intermediate radio halo and PSZ2~G080 (Abell~2018) seems to be a
halo-relic system. PSZ2~G089 and PSZ2~G080 are among the lowest-mass clusters
discovered with a radio relic and a halo-relic system, respectively. A high
($\sim30\%$) detection rate, with powerful radio emission ($P_{1.4\ {\rm
GHz}}\sim10^{23}~{\rm{W~Hz^{-1}}}$) found in most of these objects, opens up
prospects of studying radio emission in galaxy clusters over a wider mass
range, to much lower-mass systems.
