Photoionization Modelling as a Density Diagnostic of Line Emitting/Absorbing Regions in Active Galactic Nuclei

This book presents timely work on the nature of the physical processes underpinning two of the basic characteristics of the gas structure in the innermost region of Active Galactic Nuclei (AGN): ionized outflows and emission line regions. In addition, it describes physics-based methods for estimating the density of the astrophysical plasma surrounding AGN. All numerical computations of the photoionized gas employ the most advanced codes available (CLOUDY and TITAN). Calculations of the radiative transfer are based on the assumption of thermal and ionization equilibrium. Promising preliminary examples of comparison with current observations are included for several individual AGN. All of them suggest that the absorbing/emitting gas should have a density on the order of 1012 cm-3. Future observations will provide more objects to verify these results, and will allow us to put constraints on the launch radius of ionized outflows and therefore on the mass loading and kinetic energy outflow rates. These rates, in turn, are crucial to estimating whether the outflows have a significant feedback impact on star formation and metal enrichment in the interstellar medium of the host galaxy. In closing, the book discusses a representative example of applying powerful photoionization techniques to explain the complex physics of the AGN environment.

Autorentext
Dr Tek P Adhikari completed his MSc (Theoretical Physics) at Tribhuvan University in Kathmandu, Nepal in 2011. In 2018, he completed his PhD degree in Astronomy at the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences (NCAC PAS) in Warsaw, Poland. Dr Adhikari's doctoral dissertation was recognized with Distinction by the Scientific Council of the NCAC PAS for its outstanding contribution to the study of the AGN environment. In 2016, he received a Young Scientist Award from NCAC PAS for the best research paper by a Ph.D. student. He has delivered scientific talks at many international conferences and has co-authored more than 15 research publications in prestigious international journals.

Inhalt
Introduction.- Photoionization simulations of AGN environment.- The role of gas density.- Absorption Measure Distribution (AMD) in AGNs.- Intermediate line region in AGNs.- Summary and future studies.- Bibliography.