Influences of Radiation Pressures on Mass Estimates of Supermassive Black Holes in AGNs

TL;DR

This study shows that radiation pressures from free electrons and hydrogen recombination significantly affect black hole mass estimates in AGNs, potentially causing underestimations of up to 40% for high-accretion-rate sources.

Contribution

It introduces the impact of two continuum radiation pressures on black hole mass estimates, highlighting their importance often neglected in previous models.

Findings

Radiation pressures can cause underestimation of black hole masses by 30-40%.

The effect is more pronounced in AGNs with high accretion rates.

Complete radiation pressure consideration is necessary for accurate mass estimates.

Abstract

In this paper, we investigate the influences of two continuum radiation pressures of the central engines on the black hole mass estimates for 40 active galactic nuclei (AGNs) with high accretion rates. The two continuum radiation pressure forces, usually believed negligible or not considered, are from the free electron Thomson scattering, and the recombination and re-ionization of hydrogen ions that continue to absorb ionizing photons to compensate for the recombination. The masses counteracted by the two radiation pressures $M_{\rm{RP}}$ depend sensitively on the percent of ionized hydrogen in the clouds $\beta$, and are not ignorable compared to the black hole virial masses $M_{\rm{RM}}$, estimated from the reverberation mapping method, for these AGNs. As $\beta$ increases, $M_{\rm{RP}}$ also does. The black hole masses $M_{\rm{\bullet}}$ could be underestimated at least by a factor of 30--40 percent for some AGNs accreting around the Eddington limit, regardless of redshifts of sources $z$. Some AGNs at $z < 0.3$ and quasars at $z \ga 6.0$ have the same behaviors in the plots of $M_{\rm{RP}}$ versus $M_{\rm{RM}}$. The complete radiation pressures will be added as AGNs match $M_{\rm{RP}}\ga 0.3 M_{\rm{RM}}$ due to the two continuum radiation pressures. Compared to $M_{\rm{RM}}$, $M_{\rm{\bullet}}$ might be extremely underestimated if considering the complete radiation pressures for the AGNs accreting around the Eddington limit.