BLACK HOLE-BULGE RELATIONSHIPS IN BROAD-LINE ACTIVE GALACTIC NUCLEI

Open Access
Author:
Shen, Jiajian
Graduate Program:
Astronomy and Astrophysics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
August 06, 2007
Committee Members:
  • Donald P Schneider, Committee Chair
  • Daniel Vanden Berk, Committee Member
  • Pablo Laguna, Committee Member
  • Derek Brindley Fox, Committee Member
  • Douglas Cowen, Committee Member
Keywords:
  • Host Galaxy
  • Active Galactic Nuclei
  • Black Hole
  • Spectral and Imaging decomposition
Abstract:
The formation and evolution of galaxies in the universe is still poorly understood. Possible clues have come recently from studies of the apparent connection between galaxies and the massive black holes (BH) that most galaxies harbor. Historically, it has been difficult to determine both galaxy and central black hole properties for all but a small fraction of galaxies. In this thesis, spectroscopic and imaging decompositon techniques are applied to a large sample of active galaxies to simultaneously determine the host galaxy and central BH properties. The large sample size allows statistical tests to be applied to the host/black hole relationships that have not been possible previously. Using an eigenspectrum decomposition technique, we separated the host galaxy from the broad line active galactic nucleus (AGN) in a set of 4666 spectra from the Sloan Digital Sky Survey (SDSS), from redshifts near zero up to about 0.75. A sub-sample of over 900 active galaxies with high quality spectra and host galaxy dominated by an early-type (bulge) component was selected to study the host-BH relatioships. The sub-sample BH masses (MBH) (estimated by the decomposed AGN spectra), the host stellar velocity dispersions (sigma_*) and host luminosities (measured by the decomposed host galaxy spectra) are all correlated, similar to the relationships found for low-redshift, bulge-dominated galaxies. As a complement to the spectroscopic study, we performed a two-dimensional imaging decomposition analysis that separates the AGN and bulge components. With the host galaxy effective radius R_e and host galaxy photometric luminosity L_H measured from the host galaxy image, we reevaluated the correlations between the AGNs and host galaxies. Our very large sample size allows tight constraints to be placed on the mean relationships. The correlations among M_{BH}, sigma_*, and L_H in the r band are: L_H ~ {sigma_*}^{4.18+-0.27} (a Faber-Jackson relation), M_{BH} ~L_H^{0.78+-0.06} and M_{BH} ~ {sigma_*}^{3.68+-0.35}. The study of active galaxy BH and host connection in this thesis suggests some coevolution facts of the BH and the host galaxy. The host galaxies at redshifts up to z ~ 0.3 should be fully formed early-type galaxies, indicated from their following of the standard galaxy Faber-Jackson relationship. The correlations of the active galaxy relationships of M_{BH} with L_H and sigma_* indicate that the BH growth and the galaxy formation are coupled processes, and the lower power-law index indicates that the relative growth rate of the BHs are faster than that of the bulge.