Testing the Correlation between Spiral Arm Pitch Angle and Central Black Hole Mass

Abstract

In order to address the “cosmic downsizing problem,” or the underpopulation of highly massive quasars in the current epoch, the Arkansas Galaxy Evolution Survey is exploring a correlation, the M‐P relation, between the pitch angle of a galaxy’s spiral arms and the mass of its central supermassive black hole (SMBH). The goal is to add to the census of SMBH masses using only images, without relying on spectra. We present the null correlation between the pitch angle of spiral arms and redshift. The data set includes 225 galaxies from the GOODS North and South fields with redshifts out to z∼1.2. There does not appear to be any dependence of pitch angle on redshift. Consequently, if the relationship between pitch angle and SMBH mass has not evolved since z∼1.2, then the mean mass of SMBH has also remained constant. If, on the other hand, the relationship has evolved, then the mean mass has evolved inversely with the relationship. This conclusion is subject to further studies on possible selection effects. Additionally, we present preliminary results testing the M‐P relation by comparing the masses of a sample of active spiral galaxies as calculated by the pitch angle method with those calculated by the mass scaling relationship.