Using new 610 MHz and 235 MHz observations from the Giant Metrewave Radio Telescope ( GMRT ) in combination with archival GMRT and Very Large Array ( VLA ) survey data we present the radio properties of the dominant early–type galaxies in the low-richness sub-sample of the Complete Local-volume Groups Sample ( CLoGS ; 27 galaxy groups ) and provide results for the radio properties of the full CLoGS sample for the first time .
We find a high radio detection rate in the dominant galaxies of the low-richness sub-sample of 82 % ( 22/27 ) ; for the full CLoGS sample the detection rate is 87 % ( 46/53 ) .
The group-dominant galaxies exhibit a wide range of radio power , 10 ^ { 20 } - 10 ^ { 25 } W Hz ^ { -1 } in the 235 and 610 MHz bands , with the majority ( 53 % ) presenting point-like radio emission , 19 % hosting currently active radio jets , 6 % having remnant jets , 9 % being diffuse and 13 % having no detected radio emission .
The mean spectral index of the detected radio sources in the 235 - 610 MHz frequency range is found to be \alpha _ { 235 } ^ { 610 } \sim 0.68 , and \alpha _ { 235 } ^ { 1400 } \sim 0.59 in the 235 - 1400 MHz one .
In agreement with earlier studies , we find that the fraction of ultra-steep spectrum sources ( \alpha > 1.3 ) is \sim 4 % , mostly dependent on the detection limit at 235 MHz .
The majority of point-like systems are found to reside in dynamically young groups , whereas jet systems show no preference between spiral-rich and spiral-poor group environments .
The mechanical power of the jet sources in the low–richness sample groups is estimated to be \sim 10 ^ { 42 } - 10 ^ { 44 } erg s ^ { -1 } with their black hole masses ranging between 2 \times 10 ^ { 8 } - 5 \times 10 ^ { 9 } M _ { \odot } .
We confirm previous findings that , while radio jet sources tend to be associated with more massive black holes , black hole mass is not the decisive factor in determining jet activity or power .