Determination of supermassive black hole spins in local active galactic nuclei

TL;DR

This study estimates the spins of supermassive black holes in local active galactic nuclei, revealing their distribution, correlation with black hole mass and luminosity, and a decrease in spin over cosmic time, aligning with theoretical models.

Contribution

It introduces a method to estimate SMBH spins using three models and provides new observational data on spin distribution and evolution in low-redshift AGNs.

Findings

Spin decreases with cosmic time.

Spin increases with SMBH mass and luminosity.

Approximately 40% of objects have spin a > 0.75.

Abstract

We estimated the radiative efficiency and spin value for a number of local active galactic nuclei with z < 0.34 using 3 popular models connecting the radiative efficiency with such parameters of AGNs as mass of supermassive black hole, angle between the line of sight and the axis of the accretion disk and bolometric luminosity. Analysis of the obtained data shown that the spin value decreases with cosmic time, which is in agreement with results of theoretical calculations for low redshift AGNs of other authors. Also we found that the spin value increases with the increasing mass of SMBH and bolometric luminosity. This is the expected result that corresponds to theoretical calculations. Analysis of the distribution of the spin values shown a pronounced peak in the distribution in 0.75 < a < 1.0 range. ~ 40% of objects have spin a > 0.75 and ~ 50% of objects have spin a > 0.5. This results are in a good agreement with our previous results and with the results of other authors.