The interplay between the central engine and the circumnuclear environment in Compton-thin AGN

Abstract

All massive galaxies harbor a supermassive black hole (SMBH) at their galactic center. If these SMBH are actively feeding then they are called Active galactic nuclei (AGN). Their accretion system contains a corona, an accretion disk and an axisymmetric dusty torus. The torus can be connected physically and dynamically to the circumnuclear disk of the galaxy which acts as a molecular gas reservoir for material to be accreted onto the SMBH. Further, AGN can emit radiation from radio up to the gamma rays. The AGN accretion disk emits photons mostly in the optical/UV band which are Compton up-scattered in the corona to generate X-rays. If present, a jet can produce additional high-energy and Synchrotron emission. In some AGN, a huge amount of material can be stripped away from the accretion disk creating an outowing wind. These --radiation pressure, jet, wind etc.--inject energy back into the host galaxy, regulating the SMBH growth. There exist a complex interplay between the AGN feeding and feedback. Understanding this interaction between the central engine and its circumnuclear environment is vital in context of galaxy evolution. My work aims to study this interaction in low to moderately obscured (or Compton-thin) AGN using their broadband multi-epoch X-ray spectra plus other emission bands whenever appropriate. From the spectral analysis of broad-line radio galaxy 3C 109, I was able to constrain its high-energy cutoff for the first time. In another Seyfert galaxy Mrk 926, I was able to explore the origin of its soft excess, and found that a warm coronal origin was slightly preferred. Finally, I performed a joint multi-wavelength analysis with a physical torus model of a sample of Polar-scattered Seyfert 1 galaxies. I utilized their multi-epoch broadband X-ray spectra along with their infrared spectral/photometric data, and was able to constrain their torus properties. Despite being a sample of similar moderately-inclined Compton-thin AGN, I found a complex and varied distribution of gas and dust in their torus.