Oral Presentation
Most X-ray luminous AGN in the \textit{Swift}/BAT survey and a HyLIRG in an efficient gas supply environment
Presenter: Hikaru Fukuchi (Tohoku University)
H1821+643 is the most X-ray luminous non-beamed AGN of $L_\mathrm{14-150 keV} = 5.2\times 10^{45}$~erg~s$^{-1}$ in the \textit{Swift}/BAT ultra-hard X-ray survey and it is also a hyper-luminous infrared galaxy residing in the center of a massive galaxy cluster.
This suggests that both the Supermassive Black Hole (SMBH) and host galaxy are in the rapid mass assembly phase, which is quite different from the properties typically seen in cluster-centered galaxies in the local universe. Thus, H1821+643 is a rare source that can be used to study galaxy growth in a cluster.
We decompose the X-ray to IR spectral energy distribution (SED) into the AGN and starburst component using the SED fitting tool \verb|X-CIGALE| and obtain that H1821+643 consumes a large amount of cold gas ($\dot{M}_\mathrm{con}$) with $\mathrm{SFR}=(1.2 \pm 0.1) \times 10^3\ M_\odot$~yr$^{-1}$ and $\dot{M}_\mathrm{BH} = (14 \pm 1)$~$M_\odot$~yr$^{-1}$.
This high $\dot{M}_\mathrm{con}$ slightly exceeds the known cooling rate ($\dot{M}_\mathrm{cool}$) of the intra cluster medium (ICM), $\dot{M}_\mathrm{con}/\dot{M}_\mathrm{cool} \gtrsim 1$, which is one to two order magnitude higher than the typical value of other systems.
This may be achieved because the SMBH in H1821+643 has the radiation efficient accretion disk with Eddington ratio $\eddington \sim 0.2$, creating an environment where the hot gas of ICM can cool by bremsstrahlung without the energy injection by the jet.
In order to efficiently cool and consume the inflow gas from the cluster, the gas must be cooled to below 100 K. This source has a bright fine structure line of [O~{\sc{i}}] 63 $\mathrm{\mu m}$, which may play a major role as a cooling path.
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