Speaker
Description
Milliarcsecond-scale radio observations of active galactic nuclei (AGN) can help us determine the origin of their radio emission. In case of blazars, radio-loud AGN with their jets pointed close to our line of sight, most of the emission comes from the relativistically boosted jet. However, the radio emission of AGN can originate not only from the jets but from the accretion disk corona or even star formation in the host galaxy.
Balmaverde et al. (2020) compiled a list of radio and X-ray emitting sources that are presumed to be good TeV-emitting candidates (Te-REX) to be detected by the upcoming Cherenkov Telescope Array (CTA). Based on whether they show nuclear activity according to their optical spectra, these sources can be divided into two groups: BL Lacs (a subtype of blazars) and Passive Elliptical Galaxies (PEGs). We obtained Very Long Baseline Interferometry (VLBI) observations of 2 PEGs and used archival VLBI measurements of 6 BL Lacs with additional multi-wavelength data to identify the origin of the radio emission.
We showed that radio emission originates from the nuclear activity in all cases. In one source, jet-related emission is the most probable explanation, while in 5 other objects coronal radio emission may be present.