Probing the Parsec-Scale Dynamical Structure of Ionized Gas in Radio-Quiet AGN with SKA
Abstract
We systematically organize the radio-emitting components in radio-quiet active galactic nuclei (RQ AGN), including jets, accretion disk coronae, dust, ionized gas outflows, and circumnuclear star formation. We present a diagnostic framework for distinguishing these components using spectral turnovers and spectral indices produced by synchrotron self-absorption (SSA) and free-free absorption (FFA), together with brightness temperature and peak frequency. The central premise is that the observed spectral index and its spatial distribution are not unique source properties unless the observing beam is specified: changing the angular resolution changes the physical scale being sampled and therefore changes the mixture of radio-emitting components. By exploiting this scale dependence with SKA1-MID and SKA-VLBI, spatially resolved spectral-index mapping will reveal which physical processes dominate from circumnuclear star formation on 100 pc scales to jets, coronal emission, and compact ionized gas on parsec and sub-parsec scales. Through multi-frequency continuum imaging and spectral-index mapping, SKA observations will provide a multi-scale physical view of radio-quiet AGN that links radio emission mechanisms to accretion, obscuration, and feedback.
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