On the Role of Hot Feedback Mode in Active Galactic Nuclei Feedback in an Elliptical Galaxy. (arXiv:1901.07570v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Yoon_D/0/1/0/all/0/1">Doosoo Yoon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yuan_F/0/1/0/all/0/1">Feng Yuan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ostriker_J/0/1/0/all/0/1">Jeremiah P. Ostriker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ciotti_L/0/1/0/all/0/1">Luca Ciotti</a>
In AGN feedback study, it is crucial to precisely determine the accretion
rate of AGN and properly adopt the AGN physics, since they determine the AGN
radiation and wind outputs. One key feature of such an AGN physics is that,
depending on the value of the accretion rate, accretion is divided into two
modes, namely hot and cold, corresponding to below and above $2% L_{rm Edd}$
respectively. In this paper we investigate the role of the hot mode by
performing hydrodynamical numerical simulations of AGN feedback in an isolated
elliptical galaxy. We have run two test models. In one model, we always adopt
the cold mode accretion physics no matter what value the accretion rate is; in
another model, we turn off the AGN outputs once the accretion is in the hot
mode. We have calculated the AGN light curves, black hole growth, star
formation, and AGN energy duty-cycle and compared the results of these two
models with the model in which the two modes are correctly taken into account.
Important differences are found. For example, if we would adopt only the cold
mode, compared to the model considering both modes, the AGN luminosity would
become significantly smaller, the total mass of newly formed stars would become
two orders of magnitude smaller, and the fraction of energy ejected within the
high accretion regime (i.e., $L_{rm BH} > 2% L_{rm Edd}$) would be very
small ($ll 10^{-3}$), inconsistent with observations. These results strongly
indicate the importance of hot mode feedback, which is because the time
fraction of being in this mode is very large. We have also investigated the
roles of wind and radiation in the hot mode and found that usually wind is more
important than radiation; but, depending on the problem, radiation also cannot
be neglected.
In AGN feedback study, it is crucial to precisely determine the accretion
rate of AGN and properly adopt the AGN physics, since they determine the AGN
radiation and wind outputs. One key feature of such an AGN physics is that,
depending on the value of the accretion rate, accretion is divided into two
modes, namely hot and cold, corresponding to below and above $2% L_{rm Edd}$
respectively. In this paper we investigate the role of the hot mode by
performing hydrodynamical numerical simulations of AGN feedback in an isolated
elliptical galaxy. We have run two test models. In one model, we always adopt
the cold mode accretion physics no matter what value the accretion rate is; in
another model, we turn off the AGN outputs once the accretion is in the hot
mode. We have calculated the AGN light curves, black hole growth, star
formation, and AGN energy duty-cycle and compared the results of these two
models with the model in which the two modes are correctly taken into account.
Important differences are found. For example, if we would adopt only the cold
mode, compared to the model considering both modes, the AGN luminosity would
become significantly smaller, the total mass of newly formed stars would become
two orders of magnitude smaller, and the fraction of energy ejected within the
high accretion regime (i.e., $L_{rm BH} > 2% L_{rm Edd}$) would be very
small ($ll 10^{-3}$), inconsistent with observations. These results strongly
indicate the importance of hot mode feedback, which is because the time
fraction of being in this mode is very large. We have also investigated the
roles of wind and radiation in the hot mode and found that usually wind is more
important than radiation; but, depending on the problem, radiation also cannot
be neglected.
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