Other Astrophysics and Astronomy Commons^™

Effect Of Equation Of State On The Formation Of Binary Black Holes In Active Galactic Nucleus Disks, Theodore Edwards

Dissertations, Theses, and Capstone Projects

Active galactic nucleus disks have been proposed as a possibly dominant location of the mergers of binary black holes detected by gravitational wave observatories. The nonlinear interactions between stellar mass black holes and disk gas determine when binaries will form from single objects on nearby orbits. Prior work has used smoothed particle hydrodynamics models in an isothermal disk to study this problem. However, the local equation of state near the midplane of an optically thick accretion disk is adiabatic rather than isothermal, even if the radiative equilibrium temperature is azimuthally isothermal. Therefore, we investigate the use of an adiabatic equation …

Exploring The Glow Of The Universe In Gamma-Rays And Hunting Distant Agn, Changam Meenakshi Rajagopal

All Dissertations

The entirety of the γ-ray radiation permeating our Universe is encoded in the extragalactic γ-ray background. This is a superposition of resolved sources, mostly powerful relativistic jets powered by supermassive black holes, i.e., blazars, and an unresolved isotropic component, aka, the diffuse isotropic gamma-ray background (IGRB). Studying the IGRB can help unveil its composition, as well as unearth multi-messenger relationships between the intensities of PeV neutrinos, ultra high energy cosmic rays (> 1018 eV), and sub-TeV γ-rays. The comparable energy budgets of these three phenomena (neutrinos, UHECR, and γ-rays) indicates a physical connection or a common source amongst them. On …

Finding Obscure Black Hole Growth Via Spectral Energy Distribution Modeling, Randall K. Chan

Honors Theses

An active galactic nucleus (AGN) occurs when the supermassive black hole at the center of the galaxy starts to grow. We still currently do not know what triggers AGN. Theories suggest that galaxy mergers could trigger AGNs, but past research has not been able to find a correlation between x-ray detected AGNs and disturbed galaxies. The present research looks specifically at AGN not detected in the x-ray, or obscured AGN. Using a newly updated IDL code, FAST, we were able to identify potential obscured AGN through spectral energy distribution (SED) modeling. We found a total of 526 obscured AGN in …

Probing The Fitting Accuracy Of Active Galaxy Spectra, Aaron T. Line

Physics

Prior to this study, Dr. Vardha N. Bennert and collaborators selected a sample of ~100 local active galaxies to study the relationships between black hole mass and host galaxy properties. The broad Hβ width is necessary to determine black hole mass. This value is determined using a spectral decomposition code was scripted in IDL by Dr. Daeseong Park. The script fit spectral features and collected data for properties such as width of emission lines and continuum contribution percentages. The results were logged for further analysis.

To probe the accuracy of the fitting process, artificial spectra were created and fitted to …

Determining The Relationship Between The [Oiii] 5007 Å Emission Line Profile And The Stellar Velocity Dispersion In Active Galaxies, Nathaniel Milgram

Physics

The empirical relation between the stellar velocity dispersion (SVD) of the bulge and the mass of the central supermassive black hole (BH) suggests a link between host galaxy and BH evolution. For active galactic nuclei (AGNs), the BH mass (MBH) can be estimated in a straightforward way from the Doppler broadening of the broad emission lines using the so-called virial method. However, the powerful AGN continuum emission often outshines the underlying stellar absorption lines, making it difficult to measure SVD of the host galaxy. Thus, the MBH - SVD relation is difficult to establish for galaxies containing AGNs. As a …

Analysis Of The Blazar 1es1218+30.4, Timothy Wolf

Physics

I analyzed the Blazar 1ES1218+30.4 in the high energy spectrum with VERITAS telescope data. The analysis used improved the energy spectrum obtained for the blazar from a maximum of 2.49 TeV to 3.85 TeV. The flux for this point is greater than the previous fit equation predicts, indicating a possible shoulder in the EBL, or Extragalactic Background Light.