Speaker
Description
Blazars have been challenging to study at low radio frequencies due to limited sensitivity and resolution in previous surveys at these frequencies. However, the recent LOFAR surveys; LoLSS-DR1 and LoTSS-DR2, have addressed these issues enabling robust detection of known blazar counterparts. Utilising this, we examine the spectral properties of the blazar population at low frequencies. We follow this up with high resolution LOFAR-VLBI imaging of an X-ray jetted blazar OJ287. The X-ray emission from resolved knots in the jets of many blazars cannot be explained as a simple extension of the radio synchrotron spectrum. So far no general consensus has been reached on the relative dominant contribution of the different broadband-emission mechanisms at play. In particular, observing the low radio frequencies provides valuable constraints to test different emission models like IC/CMB, Synchrotron Self Compton(SSC) or second synchrotron peak. The long international baselines of LOFAR allow us to spatially resolve the individual X-ray emitting jet knots at 140MHz and to probe the previously inaccessible part of the low-energy electron population. In combination with shorter-wavelength radio in uGMRT (600 MHz), the VLA GHz regime and Chandra X-ray data, the LOFAR-VLBI data will help test and constrain the above-mentioned different emission models. Here, we present results from this project with a focus on connecting the low frequency radio to X-ray emissions in the kiloparsec scale knots in the jet. Furthermore, we present broadband SED modeling analysis for these knots, thereby understanding the physical properties of the underlying electron population. Our analysis highlights the potential of low-frequency, high-resolution radio observations to bridge the gap between radio and X-ray regimes in blazar jets.
