Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Arts and Sciences


Physics and Astronomy

First Advisor

Dr. Gary Ferland


Active galactic nuclei (AGNs) are located at the centers of massive galaxies and are the most luminous objects in the universe. Each AGN embeds a super-massive black hole which produces outflows of gas, or winds. These winds are important because they provide a reasonable physical basis for the connections between the black hole and the properties of their host galaxy. While AGNs have been extensively studied, several fundamental questions about them are yet to be answered. These include the structure and dynamics of the central source and their winds, and questions regarding the evolution of these galaxies.

NGC 5548 is a bright and well-studied AGN that has been the target of many monitoring campaigns since 1987. The most extensive observations were in 2013 and 2014, in which its emission and absorption lines behaved in an anomalous way that had never before been seen. For a two-month period during the observations, emission and absorption lines did not respond to the variations of the continuum – the HST team said that the spectral lines had “gone on holiday”. The main goal of my thesis is to model the pan-spectral data available for the NGC 5548 not only to explain the abnormal holiday, but also to use the data as a laboratory to investigate the inner structure of the AGNs and their evolution.

Here I explain the physics by which the variations of a disk wind produce the observed holiday. The disk wind acts as a shield between the central source and the clouds that produce the emission and absorption lines. I simulate the behavior of the wind to explain the holiday, and also investigate and model the general characteristics of such winds to predict their effects on the observations. My newly proposed models lead to novel tools to detect the footprint of the disk winds in the observations and track their evolution. This project is a systematic study of UV and X-ray spectroscopic signatures of the wind in the NGC 5548 and is widely applicable to the family of AGNs. Although the comprehensive data set that is used here belongs to one AGN, the results are applicable to all AGNs.

Digital Object Identifier (DOI)

Funding Information

1- Huffaker travel scholarship- Department of physics and astronomy - 2017

2- MacAdam fellowship- Department of physics and astronomy-2019-2020

3- Space Telescope Science Institute, HST-AR-13914, 2015-2018

4- Space Telescope Science Institute, HST-AR- 15018, 2017-2020

5- National Science Foundation, AST 1816537, 2018-2021