Radio continuum emission and HI gas accretion in the NGC 5903/5898
  compact group of early-type galaxies
  We discuss the nature of the multi-component radio continuum and HI emission
associated with the nearby galaxy group comprised of two dominant ellipticals,
NGC 5898 and NGC 5903, and a dwarf lenticular ESO514-G003. Striking new details
of radio emission are unveiled from the 2nd Data Release of the ongoing
TIFR.GMRT.SKY.SURVEY (TGSS) which provides images with a resolution of ~ 24
arcsec x 18 arcsec and a typical rms noise of 5 mJy at 150 MHz. Previous radio
observations of this compact triplet of galaxies include images at higher
frequencies of the radio continuum as well as HI emission, the latter showing
huge HI trails originating from the vicinity of NGC 5903 where HI is in a
kinematically disturbed state. The TGSS 150 MHz image has revealed a large
asymmetric radio halo around NGC 5903 and also established that the dwarf SO
galaxy ESO514-G003 is the host to a previously known bright double radio
source. The radio emission from NGC 5903 is found to have a very steep radio
spectrum ({\alpha} ~ -1.5) and to envelope a network of radio continuum
filaments bearing a spatial relationship to the HI trails. Another noteworthy
aspect of this triplet of early-type galaxies highlighted by the present study
is that both its radio loud members, namely NGC 5903 and ESO514-G003, are also
the only galaxies that are seen to be connected to an HI filament. This
correlation is consistent with the premise that cold gas accretion is of prime
importance for triggering powerful jet activity in the nuclei of early-type
galaxies.
