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Register a new userInfluences of Radiation Pressures on Mass Estimates of Supermassive Black Holes in AGNs
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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.
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Supermassive black holes reside in the nuclei of most galaxies. Accurately determining their mass is key to understand how the population evolves over time and how the black holes relate to their host galaxies. Beyond the local universe, the mass is commonly estimated assuming virialized motion of gas in the close vicinity to the active black holes, traced through broad emission lines. However, this procedure has uncertainties associated with the unknown distribution of the gas clouds. Here we show that the comparison of black hole masses derived from the properties of the central accretion disc with the virial mass estimate provides a correcting factor, for the virial mass estimations, that is inversely proportional to the observed width of the broad emission lines. Our results suggest that line-of-sight inclination of gas in a planar distribution can account for this effect. However, radiation pressure effects on the distribution of gas can also reproduce our findings. Regardless of the physical origin, our findings contribute to mitigate the uncertainties in current black hole mass estimations and, in turn, will help to further understand the evolution of distant supermassive black holes and their host galaxies.
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