Ph.D. Candidate: Anna Ogorzalek
Research Advisor: Steven W. Allen
Date: Tuesday, July 9th 2019
Time: 11:00 AM
Location: Varian 355
Title: Probing the physics of AGN feedback with high resolution X-ray spectroscopy
Active galactic nuclei (AGN) significantly impact the evolution of their host galaxies, as they can prevent star formation by either expelling large fractions of gas with wide-angle outflows, or by heating up the halo gas with jets. However, how the AGN energy is transferred to the galaxy in either of these feedback modes is still not known. In this talk I will summarize my dissertation research, which involves novel applications of modern inference techniques to high resolution X-ray spectra in order to gain new insights into the physical processes behind AGN feedback.
First, I will introduce our improved Bayesian framework for the self-consistent modelling of deep spectra from nearby AGN with X-ray detected outflows. For the first time we are able to perform robust model selection, while keeping all of the parameter space open. We applied our approach to a new, deep Chandra High Energy Transmission Grating observation of the Seyfert-1 galaxy NGC 4051, where we successfully mapped multiple absorbing components moving at ~few 1000 km/s. We obtained one of the tightest outflow density constraints to date, thereby measuring wind’s impact on the galaxy.
Second, I will present our unprecedented measurements of the gas turbulent velocities in the cores of 13 nearby giant elliptical galaxies, which we obtained by statistically combining resonant scattering and direct line broadening techniques applied to deep XMM-Newton Reflection Grating Spectrometer observations. This allowed us to explore the precise nature of the hot gas motions in massive galaxies and constrain models of AGN feedback in these objects.
I will then discuss how we have successfully applied our resonant scattering analysis to the first X-ray microcalorimeter observation, the Hitomi Perseus Cluster spectrum. This allowed us to place independent constraints on the hot gas turbulence in a galaxy cluster. Additionally, our technique provided unique clues to the three dimensional structure of the gas velocity field.
I will conclude my talk by discussing the potential of both techniques and future research directions within the context of the upcoming high spectral resolution X-ray missions, such as XRISM, ATHENA. Arcus, and Lynx.