Physics Department

Degree Name

BA in Physics




Vardha N. Bennert


Active Galactic Nuclei (AGNs) provide a unique opportunity to measure the mass of supermassive black holes located in the centers of their host galaxies. This enables studying the scaling relations between the mass of the black hole and the properties of the host galaxy.

In this thesis, we present an investigation of the relationship between black hole masses and the host galaxy bulge and total luminosity for a pilot sample of 15 objects imaged in the near-infrared with the 8m telescope of Gemini North observatory. We perform a 2D decomposition of the host galaxies using the software Galfit and obtain photometric measurements of the components. The high spatial resolution of the Gemini images allows for a detailed study of the different host galaxy components, in particular distinguishing between classical and pseudo-bulges in the presence of a bright AGN point source. In the literature, there is controversy about whether the mass of the black hole scales more closely with classical or pseudo bulges. Shedding light on this issue is crucial to our understanding of the underlying physical driver of the relations.

In this study, the improved near-infrared images resulted in very different host galaxy parameters compared to those published in Bennert et al. 2015 based on images from the Sloan Digital Sky Survey. Our findings suggest that the sample of active galaxies reside in galaxies that are over-luminous compared to quiescent galaxies. Furthermore, we find that pseudo bulges are on the black-hole-mass - bulge-luminosity relation. However, for a handful of objects, the Gemini images do not have sufficient resolution to resolve the (pseudo-) bulge. Therefore, follow-up observations with the Hubble Space Telescope are currently underway.