Abstract
The innermost regions of radio loud Active Galactic Nuclei (AGN) jets are heavily affected by synchrotron self-absorption, due to the strong magnetic fields and high particle densities in these extreme zones. The only way to overcome this absorption is to observe at sub-millimeter wavelengths, although polarimetric observations at such frequencies have so far been limited by sensitivity and calibration accuracy. However, new generation instruments such as the Atacama Large mm/sub-mm Array (ALMA) overcome these limitations and are starting to deliver revolutionary results in the observational studies of AGN polarimetry. Here we present an overview of our state-of-the-art interferometric mm/sub-mm polarization observations of AGN jets with ALMA (in particular, the gravitationally-lensed sources PKS 1830−211 and B0218+359), which allow us to probe the magneto-ionic conditions at the regions closest to the central black holes.
Highlights
IntroductionSuper massive black holes (SMBHs) are among the most exotic objects in the known Universe
Super massive black holes (SMBHs) are among the most exotic objects in the known Universe.Relativistic outflows—related to accretion discs—form in their immediate neighborhood via processes that are not yet well understood (e.g., [1,2]); processes that directly involve the action of the main pillars of modern physics: from general relativity to quantum mechanics
The rapid time variability of the electric vector position angle (EVPA) and its eventual correlation with γ-rays can be explained by shock-compression effects or from pseudo-random variability induced by turbulence, related to the regions of γ-ray up-scattering
Summary
Super massive black holes (SMBHs) are among the most exotic objects in the known Universe. The main observational challenge for the study of these different scenarios and models is the detection and monitoring of polarized emission at very high resolutions both in time and space). It is needless to say that the eventual detection of RM at submm wavelengths, and the study of its time and frequency dependence, is a precious source of information to probe these elusive regions in radio-loud AGN. In the former case, RM would depend on frequency, RM(ν); in the latter, it would rather be constant in the submm spectral region
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