The accretion-ejection coupling in Active Galactic Nuclei: a radio perspective

In Webseminar by admin

Wednesday 10 February 2021 11 CET; Elia Chiaraluce, INAF/IAPS

The many ejection features observed in Active Galactic Nuclei (AGN), like jets, outflows and winds, on different scales and strengths, are thought to strongly influence the evolution of the host galaxy. A thorough characterisation of them is required to build more robust galaxy evolutionary models in the framework of AGN-host galaxy feedback theories. Radio emission, being highly penetrative and less affected by absorption, provides an ideal way of sampling the ejection physics of AGN and to study the connection with properties of the accretion flow. In this talk we will present observations for a number of Radio-Quiet (RQ) sources, which allow to characterise the ejection features without the emission being dominated by relativistic jets, as in Radio-Loud (RL) sources. We considered two samples of nearby AGN, one of low-luminosity AGN (LLAGN), with log L/Ledd < -3, and one of hard-X-rays selected AGN (HXAGN), with -2.5 < log L/Ledd < -0.5. For these sources we present the results of an extensive observational campaign with the Jansky Very Large Array (JVLA) in the frequency range 1.4 – 45 GHz, with a resolution smaller than ~ arcsec. The high-sensitivity and the high-resolution allow us to reveal compact as well extended, diffuse regions and jet-like features, while the wide frequency coverage allows us to build Spectral Energy Distributions (SEDs) for the emitting components, a crucial ingredient to constrain the mechanisms responsible for the radio emission. We have found high detection fractions (i.e. > 80 per cent), although the non-detection of some sources poses intriguing questions on their radio silent nature. The radio-loudness, the morphology and wide-frequency SEDs of the detected sources will be discussed in light of the mechanisms invoked to explain radio emission in RQ AGN. For a number of them, we will present a multi-wavelength approach which allowed to put more stringent constraints on the involved physical mechanisms. The results of the study of radio-X-rays correlations will be presented in light of AGN-XRB analogy theories. Finally, the above evidence will be discussed to understand the connection between the ejection features of AGN and the fundamental propertied of the accretion state.