Speaker
Description
Blazars, the subclass of jetted AGN with their outflow axes closely aligned to our line of sight, comprise one of the most energetic, long-lived phenomena in the Universe. They are among the main constituents of the high-energy sky, especially in gamma-rays and up to TeV energies, and one of possible sources of astrophysical neutrinos. The low-energy part of their SEDs is understood as incoherent synchrotron emission from their jets, which spans from radio to optical, UV or even X-rays and is both linearly and circularly polarized. On top of their persistent broadband emission, blazar jets often show pronounced variability across the electromagnetic spectrum with timescales from days/months down to minutes.
In this presentation, we will demonstrate our efforts to capture the complex phenomenology of blazar jets through dedicated multi-wavelength polarization monitoring programs using several large radio facilities operating at mm and cm wavelengths, such as POLAMI, SMAPOL, BEAM-ME and QUIVER. Our observations, which cover two decades of frequency (2.6 GHz — 230 GHz), are used to follow the flux density and polarization variations of our blazar sample with a ~3-week cadence. The linear and circular polarization parameters and their variability are used to constrain the jet physical conditions, such as the magnetic field strength and topology, the plasma composition and energetics, and study their dynamics. In addition, we respond to selected neutrino alerts and coordinate with multi-wavelength campaigns, including IXPE or MAGIC, to identify the high-energy emission mechanism of blazar jets based on the expected multi-band polarization characteristics.