Principal Investigator: Monica Valluri
PI Institution: University of Michigan
Investigators
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Title: Quantifying the Bias in the Masses of Supermassive Black Holes in Barred Galaxies
Cycle: 22
Abstract
Recent studies of simulations of barred galaxies with supermassive black holes {BH} show that a bar can cause an increase in the central line-of-sight velocity dispersion {sigma} of about 7-12% - an increase that is consistent with the average offset observed for barred galaxies relative to unbarred ones. A more serious consequence of the presence of a bar is that its unique orbital structure {the combination of the radially biased bar orbits and the high bar pattern speed}, results in a high central velocity dispersion but negative 4th Gauss-Hermite parameters, even in the vicinity of the BH. This unique combination of kinematical parameters can result in a systematic over-estimate of the BH mass - if the bar is modelled as axisymmetric. Although nearly 60% of spiral/SO galaxies with existing stellar dynamically BH masses are in barred galaxies, their masses have been derived using axisymmetric models! An overestimate of BH mass in barred disks would erase morphological differences between the BH scaling relations of disks and ellipticals, which could be crucial to understanding the co-evolution of BHs and their host galaxies. In this theory proposal we will use N-body simulations to generate mock kinematic datasets {STIS, FOS and ground based IFU} for barred disk galaxies, model them with an axisymmetric orbit superposition code, and thereby quantify the magnitude of the bias in existing BH mass measurements. This analysis will provide crucial input for developing new and accurate methods for determining BH masses in galaxies of different morphological types, thereby revealing the true extent of intrinsic differences in the supermassive BH scaling relationships.