Skip to Main Content
 

Global Search Box

 
 
 

ETD Abstract Container

Abstract Header

Outflow and Accretion Physics in Active Galactic Nuclei

McGraw, Sean Michael
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1469701247

Abstract Details

2016, Doctor of Philosophy (PhD), Ohio University, Physics and Astronomy (Arts and Sciences).
This dissertation focuses on placing observational constraints on outflows and accretion disks in active galactic nuclei (AGN) for the purpose of better understanding the physics of super-massive black holes (SMBHs) and their evolution with the host galaxy over cosmic time. Quasar outflows and their importance in SMBH–host galaxy co-evolution can be further understood by analyzing broad absorption lines (BALs) in rest-frame UV spectra that trace a range of wind conditions. We quantify the properties of the flows by conducting BAL variability studies using multiple-epoch spectra acquired primarily from MDM Observatory and from the Sloan Digital Sky Survey. Iron low-ionization BALs (FeLoBALs) are a rare type of outflow that may represent a transient phase in galaxy evolution, and we analyze the variations in 12 FeLoBAL quasars with redshifts between 0.7 < z < 1.9 and rest frame timescales between 10 d to 7.6 yr. We investigate BAL variability in 71 quasar outflows that exhibit P V absorption, a tracer of high column density gas (i.e. NH > 1022 cm-2), in order to quantify the energies and momenta of the flows. We also characterize the variability patterns of 26 quasars with mini-BALs, an interesting class of absorbers that may represent a distinct phase in the evolution of outflows. Low-luminosity AGN (LLAGN) are important objects to study since their prominence in the local Universe suggest a possible evolution from the quasar era, and their low radiative outputs likely indicate a distinct mode of accretion onto the SMBH. We probe the accretion conditions in the LLAGN NGC 4203 by estimating the SMBH mass, which is obtained by modeling the 2-dimensional velocity field of the nebular gas using spectra from the Hubble Space Telescope. We detect significant BAL and mini-BAL variability in a subset of quasars from each of our samples, with measured rest-frame variability time-scales from days to years and over multiple years on average. Variable wavelength intervals are associated with high-ionization species such as C IV and N V, low-ionization lines including Mg II and Al III, and ground and excited states from Fe II multiplets. The detected BAL and mini-BAL variations in a subset of sources provide evidence supporting scenarios involving either transverse motions of gas or ionization changes within the absorbers. We conclude that some outflows in our samples likely exist on the order of 0.01–1 pc from the SMBH, and the possibility remains that we are tracing outflowing gas on larger scales within limits ranging from <10 pc to <1 kpc from the central source. We estimate outflow kinetic luminosities between 106 and 1 times the bolometric luminosity of the quasar, indicating that the BAL outflows we probe likely possess a range of energies and only some absorber energies are likely sufficient for AGN feedback processes. We estimate the SMBH mass in the LLAGN in NGC 4203 to be 1.1x107 solar masses within a factor of 2. This mass estimate in conjunction with theoretical predictions is consistent with the existence of a two-component accretion flow in the nucleus of NGC 4203, consisting of a hot, advection-dominated torus at small radii connected with a thin, radiatively efficient disk at larger scales. These results provide a significant increase in the information available for quasar outflow properties and the conditions in low-luminosity accretion disks, and will inform future observational and theoretical studies that attempt to construct a more complete picture of AGN and their e ffects on the surrounding environments.
Joseph Shields (Advisor)
Douglas Clowe (Committee Member)
Douglas Green (Committee Member)
Madappa Prakash (Committee Member)
251 p.
Astronomy; Astrophysics
active galaxies; quasar outflows; broad absorption lines; supermassive black holes; accretion disks; AGN; BALs; LLAGN; mini-BALs; FeLoBALs; NGC 4203

Recommended Citations

Citations

  • McGraw, S. M. (2016). Outflow and Accretion Physics in Active Galactic Nuclei [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1469701247

    APA Style (7th edition)

  • McGraw, Sean. Outflow and Accretion Physics in Active Galactic Nuclei. 2016. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1469701247.

    MLA Style (8th edition)

  • McGraw, Sean. "Outflow and Accretion Physics in Active Galactic Nuclei." Doctoral dissertation, Ohio University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1469701247

    Chicago Manual of Style (17th edition)

ohiou1469701247
346
© 2016, all rights reserved.
This open access ETD is published by Ohio University and OhioLINK.