Oral Presentation
Metallicity dependence of line-driven AGN disc winds and implications for black hole growth
Presenter: Mariko Nomura (Hirosaki University)
Supermassive black holes are thought to grow from low-mass seed black holes through mass accretion, yet the detailed evolutionary processes remain uncertain. Disk winds launched from accretion disks can reduce the mass accretion rate onto the black hole by extracting mass from the disk, and may therefore suppress black hole growth. In this work, we focus on disk winds accelerated by the radiation force due to absorption of ultraviolet (UV) radiation through line transitions of metals (so-called line force).
By investigating the dependence of the mass-loss rate of line-driven disk winds on black hole mass and metallicity, we quantitatively evaluate how disk winds delay black hole growth over the course of black hole and galaxy evolution. Here, metallicity is used as an indicator of galaxy evolution. We find that, assuming an evolutionary scenario in which metallicity increases with black hole mass, line-driven winds can prolong the black hole growth timescale by a factor of 1.6 compared to the no-wind case (Nomura et al. 2021).
Observationally, a positive correlation between the metallicity of the broad-line region (BLR) and the outflow strength in active galactic nuclei has been reported (Wang et al. 2012). In the era of the Subaru Prime Focus Spectrograph (PFS), such relationships between metallicity and outflows are expected to be investigated in much greater detail. We also discuss prospects for testing and validating our model through comparisons with future observations.
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