Time-dependent Photoionization Modeling of Warm Absorbers in Active Galactic Nuclei

Time-dependent Photoionization Modeling of Warm Absorbers in Active Galactic Nuclei
Author: Dev Raj Sadaula
Publisher:
Total Pages: 0
Release: 2022
Genre: Active galactic nuclei
ISBN:

Download Time-dependent Photoionization Modeling of Warm Absorbers in Active Galactic Nuclei Book in PDF, Epub and Kindle

Warm absorber spectra are bound-bound and bound-free absorption features, seen in the X-ray and UV spectra from many active galactic nuclei (AGN). The widths and centroid energies of these features indicate they occur in outflowing gas moving with hundreds to thousands of km/s. Depending upon the energy and momentum of the outflow, it can affect the gas within the host galaxy. Thus, warm absorbers’ mass and energy budgets are of great interest. Estimates for these properties depend on models that connect the absorption features' observed strengths with the density, composition, and ionization state of the absorbing gas. Such models assume that the ionization and heating of the gas are determined primarily by the strong continuum radiation from near the central black hole. They also assume that the various heating, cooling, ionization, and recombination processes are in a time-steady balance. However, this assumption may not be valid, owing to the intrinsic time-variability of the illuminating continuum or other factors like sudden adiabatic expansion and gas moving with high speed, which changes the cloud environment. Understanding outflowing gas, including warm absorbers, is crucial for understanding the AGN. We study the properties of such outflow exposed to the highly variable ionizing source using time-dependent calculations, which is different from equilibrium modeling commonly approached in modeling the photoionized gas. To model the outflow, we numerically solved the time-dependent forms of the balance equations for ionization, internal energy, and radiative transfer in a self-consistent manner. A new computer code is deployed to investigate the properties and associated spectrum for various warm absorber models. This study presents models for warm absorbers which follow the time dependence of the ionization, temperature, and radiation field in gas clouds in response to a changing continuum illumination. We show that the effects of time variability are essential over a range of parameters and that time-dependent models differ from equilibrium models in meaningful ways. Thus time-dependent effects should be included in models that derive properties of warm absorber outflows.

The Variability of Warm Absorbers in Active Galactic Nuclei

The Variability of Warm Absorbers in Active Galactic Nuclei
Author: Robert Ross Gibson
Publisher:
Total Pages: 184
Release: 2006
Genre:
ISBN:

Download The Variability of Warm Absorbers in Active Galactic Nuclei Book in PDF, Epub and Kindle

(Cont.) Either multiple factors influence line strength on observable time scales, or the line of sight to the central source varies over time through a structured absorber. In the third study, we survey spectra from the HETG data archive. We model the normalized excess variance (NEV) spectrum of a varying WA and find that it does not explain high-energy (> 2 keV) spectral variation, nor does it generally fit NEV spectra at lower energies (

High-Resolution X-ray Spectroscopy

High-Resolution X-ray Spectroscopy
Author: Cosimo Bambi
Publisher: Springer Nature
Total Pages: 425
Release: 2023-09-01
Genre: Science
ISBN: 9819944090

Download High-Resolution X-ray Spectroscopy Book in PDF, Epub and Kindle

NASA's Chandra X-ray Observatory and ESA's XMM-Newton Observatory have been the pioneering satellites for studying the Universe with X-rays and the cornerstone of X-ray spectroscopy since their launches more than 20 years ago. The onboard gratings provide us a unique opportunity to distinguish individual spectral lines from different atoms thanks to their high energy resolutions. Enormous discoveries have been achieved by these two missions when observing a variety of X-ray-emitting astronomical objects, such as black holes, supernova remnants, clusters of galaxies, and stars. However, the data are limited to fairly bright X-ray sources. The recent JAXA's mission Hitomi opened a new window of high-resolution X-ray spectroscopy thanks to its onboard X-ray calorimeter. Although this mission was shortly terminated due to a mishap, Hitomi left behind a few sets of observations awaiting more data mining. The first half of this book introduces the history of high-resolution X-ray spectroscopy and different generations of X-ray spectrometers. A tutorial guide on how to reduce, analyze, and understand the astronomical data from Chandra, XMM-Newton, and Hitomi is also included. The second half of the book reviews past results obtained by the high-resolution spectrometers on these missions on multiple topics and discusses possible discoveries by upcoming missions in the next decade.

The Physics and Evolution of Active Galactic Nuclei

The Physics and Evolution of Active Galactic Nuclei
Author: Hagai Netzer
Publisher: Cambridge University Press
Total Pages: 369
Release: 2013-09-16
Genre: Science
ISBN: 1107021510

Download The Physics and Evolution of Active Galactic Nuclei Book in PDF, Epub and Kindle

A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.