TELAMON: Effelsberg Monitoring of AGN Jets with Very-High-Energy Astroparticle Emissions -- Polarization properties

TL;DR

The TELAMON program uses the Effelsberg telescope to monitor AGN jets, focusing on polarization properties at high radio frequencies to gain insights into their emission mechanisms and relation to astroparticle phenomena.

Contribution

This study provides the first detailed polarization analysis of TeV-emitting AGN and neutrino-associated sources at multiple high radio frequencies, revealing polarization levels and variability.

Findings

82% of sources are significantly polarized at 7 mm

58% of sources are significantly polarized at 20 mm

Most sources show mean fractional polarization below 5%

Abstract

We present recent results of the TELAMON program, which is using the Effelsberg 100-m telescope to monitor the radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, namely TeV blazars and neutrino-associated AGN. Our sample includes all known Northern TeV-emitting blazars as well as blazars positionally coincident with IceCube neutrino alerts. Polarization can give additional insight into the source properties, as the polarized emission is often found to vary on different timescales and amplitudes than the total intensity emission. Here, we present an overview of the polarization properties of the TeV-emitting TELAMON sources at four frequencies in the 20 mm and 7 mm bands. While at 7 mm roughly $82\,\%$ of all observed sources are found to be significantly polarized, for 20 mm the percentage is $\sim58\,\%$. We find that most of the sources exhibit mean fractional polarizations of $<5\%$, matching the expectations of rather low polarization levels in these sources from previous studies at lower radio frequencies. Nevertheless, we demonstrate examples of how the polarized emission can provide additional information over the total intensity.