The low-frequency radio emission in blazar PKS2155-304
  We report radio imaging and monitoring observations in the frequency range
0.235 - 2.7 GHz during the flaring mode of PKS 2155-304, one of the brightest
BL Lac objects. The high sensitivity GMRT observations not only reveal extended
kpc-scale jet and FRI type lobe morphology in this erstwhile `extended-core'
blazar but also delineate the morphological details, thanks to its arcsec scale
resolution. The radio light curve during the end phase of the outburst measured
in 2008 shows high variability (8.5%) in the jet emission in the GHz range,
compared to the lower core variability (3.2%) seen at the lowest frequencies.
The excess of flux density with a very steep spectral index in the MHz range
supports the presence of extra diffuse emission at low frequencies. The
analysis of multi wavelength (radio/ optical/ gamma-ray) light curves at
different radio frequencies confirms the variability of the core region and
agrees with the scenario of high energy emission in gamma-rays due to inverse
Compton emission from a collimated relativistic plasma jet followed by
synchrotron emission in radio. Clearly, these results give an interesting
insight of the jet emission mechanisms in blazars and highlight the importance
of studying such objects with low frequency radio interferometers like LOFAR
and the SKA and its precursor instruments.
