Black hole scaling relations and feedback in dwarf galaxies

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Montana State University - Bozeman, College of Letters & Science


Over the past decade the discovery of a population of dwarf galaxies which host massive black holes (BH) has prompted the study of how these systems interact, grow and evolve. To address these questions I first present a new relationship between central black hole mass and host galaxy stellar bulge mass extending to the lowest BH masses known in dwarf galaxies (MBH < or ~ 10 5 M circle dot, M* ~ 10 9 M circle dot). I have obtained Hubble Space Telescope imaging of seven dwarf galaxies with optically selected broad-line active galactic nuclei (AGNs) and BH mass estimates from single-epoch spectroscopy. I perform modeling to decompose the structure of these galaxies and find that the majority have an inner bulge/pseudo-bulge component with an exponential disk that dominates the total stellar mass. Using the modeling results, I determine the stellar mass of each photometric component in each galaxy. I determine the M BH - M bulge relation using a total of 12 dwarf galaxies hosting broad-line AGNs, along with a comparison sample of 125 higher-mass galaxies. I find a strong correlation between BH mass and bulge mass which is in good agreement with correlations found previously when only considering higher-mass systems. Second, I investigated the role of AGN feedback in dwarf galaxies by studying Henize 2-10, a dwarf starburst galaxy previously reported to have a central massive black hole. At a distance of ~9 Mpc, it presents an opportunity to resolve the central region and determine if there is evidence for a black hole outflow impacting star formation. I found a ~150 pc long ionized filament connecting the region of the black hole with a site of recent star formation. Spectroscopy reveals a sinusoid-like position-velocity structure that is well described by a simple precessing bipolar outflow. I conclude that this black hole outflow triggered the star formation. The results from the work presented in this thesis show that the coevolution of massive BHs and their host galaxies extends into the lowest mass regime and that AGN feedback plays an important and complex role in dwarf galaxies.




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