The Morphology of Dwarf Galaxies Hosting Variability Selected AGN

Active galactic nuclei (AGN) are a class of highly energetic objects observed at the center of galaxies. AGN activity is attributed to the presence of a massive black hole (MBH). While MBHs are ubiquitous in massive galaxies, “lighter” MBHs are difficult to find and study. These “lighter” BHs, known as intermediate mass black holes (IMBH), are key to constraining different theories of MBH formation and growth. One method of studying these objects is to search for AGN in dwarf galaxies. Understanding the galactic environment in which AGNs reside can provide insights to the local population of IMBHs. Galactic properties such as stellar mass have been shown to scale with black hole mass in more massive galaxies, it is unclear what galactic properties are linked to the presence of a black hole and if they continue to scale in the low mass regime. We obtained detailed optical imaging from the Hubble Space Telescope (HST) of eight low-mass galaxies hosting AGN. Using a 2D parametric fitting software, GALFIT, we characterize the host morphology, measure AGN luminosity and black hole mass, and compare these results to other populations of AGN host galaxies. In comparison to other samples of active dwarf hosts, this sample has similar morphology, but with a higher rate of irregular morphology and this sample has lower AGN luminosity and lower BH mass in comparison dwarf AGN selected through optical spectroscopy. Our detailed imaging analysis shows that variability selection of AGN has the potential to find lower mass black holes and lower luminosity AGN than optical spectroscopy.