Hello！
Some questions want to bother you.I wonder whether the accretion process of SMBHs is a direct result of hydrodynamic simulation, or is artificially modeled like black hole feedback? Because I wanted to use TNG simulation to study some of the physics of SMBH accretion.
In addition, I noticed the paper Weinberger et al.(2017) mentioned 'for massive black holes at late times,the accretion rate is self-regulated' at Section2.2,can this be understood to mean that even if there is an artificial estimate of the black hole accretion rate, it is possible to treat black hole accretion as a natural process that is not affected by artificial setting at a later stage?If so, when does this 'self-regulated ' occur?(after which snapshot or redshift?)
The last one is how to know if one SMBH has undergone merger and which two are the progenitor?(I saw Weinberger et al.(2017) mentioned'we do not use the subhalo merger tree,but rather the merger tree of the SMBHs themselves',so that is mean in addition to subhalo merger tree,there's SMBH merger tree,how could I find them)
Thank you very much!
Dylan Nelson
21 Jul
The gas accretion on to SMBHs is a model, as described in Weinberger+17. In essence, we assume Bondi accretion, with several minor additional details.
I believe that the mention of "self-regulation" suggests an outcome of the simulation, rather than in input. For example, if a galaxy loses its gas for whatever reason, then the SMBH will no longer have any gas to accrete. This will occur for some galaxies, and not others, and is not assumed, but is an outcome. I hope that makes it more clear.
So it means the 'self-regulation' is not modelled at first,but a natural result of the accretion model,right?
And I also want to ask do the analysis results of black hole accretion using the TNG simulation data has generality?Or in other words,can I obtain a model-independent relation of accretion and galaxy properties?
Dylan Nelson
22 Jul
It is not a simple question, I would say the self-regulated nature of SMBH accretion is a mixture of the model assumptions combined with the evolving gas distribution in the simulated galaxies.
The second question is also not simple. I would say that no theory, and no simulation, provides model-independent results. All results depend on the model. The way to say that a result is model-independent is to check that you obtain the same result with many other models (simulations).
怡远 张
9 Aug
Thank you! I could probably understand the meaning of 'self-regulation'.
I saw the BH accretion rate is defined as the minimum values of Bondi accretion rate and Eddington accretion rate in Weinberger+17, so does that mean in TNG simulation no distinction is made between 'quasar mode' and ' radio mode' for accretion rate ?(although there are two types feedback)
But I found for some BHs,the accretion rate equals neither Bondi accretion rate nor Eddington accretion rate,why does this happen?
Dylan Nelson
9 Aug
TNG assumes a Bondi accretion model, so the accretion rate is always equal to the Bondi rate (limited to a maximum value of the Eddington rate).
怡远 张
9 Aug
It seems to be the case for the majority of them, but there are still some black holes whose accretion rates are not equal to the Bondi rate or Eddington rate.The Fig1 shows part of this situation,and you can try il.snapshot.loadSubhalo('./sims.TNG/TNG100-1/output/',99,32,5,['BH_Mdot','BH_MdotBondi','BH_MdotEddington'])
for example(whose results shown in Fig2,here accretion rate=0.00136819,Bondi rate=0.0063076,Eddington rate=0.17454475)
There are a few extra complications of the model, beyond Bondi. This is true, and often we overlook them.
In this case, I believe the difference will be the "external gas pressure" criterion, described in Vogelsberger+13 (Eqn. 23 and surrounding discussion).
Hello！
Some questions want to bother you.I wonder whether the accretion process of SMBHs is a direct result of hydrodynamic simulation, or is artificially modeled like black hole feedback? Because I wanted to use TNG simulation to study some of the physics of SMBH accretion.
In addition, I noticed the paper Weinberger et al.(2017) mentioned 'for massive black holes at late times,the accretion rate is self-regulated' at Section2.2,can this be understood to mean that even if there is an artificial estimate of the black hole accretion rate, it is possible to treat black hole accretion as a natural process that is not affected by artificial setting at a later stage?If so, when does this 'self-regulated ' occur?(after which snapshot or redshift?)
The last one is how to know if one SMBH has undergone merger and which two are the progenitor?(I saw Weinberger et al.(2017) mentioned'we do not use the subhalo merger tree,but rather the merger tree of the SMBHs themselves',so that is mean in addition to subhalo merger tree,there's SMBH merger tree,how could I find them)
Thank you very much!
The gas accretion on to SMBHs is a model, as described in Weinberger+17. In essence, we assume Bondi accretion, with several minor additional details.
I believe that the mention of "self-regulation" suggests an outcome of the simulation, rather than in input. For example, if a galaxy loses its gas for whatever reason, then the SMBH will no longer have any gas to accrete. This will occur for some galaxies, and not others, and is not assumed, but is an outcome. I hope that makes it more clear.
As for SMBH mergers, this supplementary data catalog attempts to provide this information.
So it means the 'self-regulation' is not modelled at first,but a natural result of the accretion model,right?
And I also want to ask do the analysis results of black hole accretion using the TNG simulation data has generality?Or in other words,can I obtain a model-independent relation of accretion and galaxy properties?
It is not a simple question, I would say the self-regulated nature of SMBH accretion is a mixture of the model assumptions combined with the evolving gas distribution in the simulated galaxies.
The second question is also not simple. I would say that no theory, and no simulation, provides model-independent results. All results depend on the model. The way to say that a result is model-independent is to check that you obtain the same result with many other models (simulations).
Thank you! I could probably understand the meaning of 'self-regulation'.
I saw the BH accretion rate is defined as the minimum values of Bondi accretion rate and Eddington accretion rate in Weinberger+17, so does that mean in TNG simulation no distinction is made between 'quasar mode' and ' radio mode' for accretion rate ?(although there are two types feedback)
But I found for some BHs,the accretion rate equals neither Bondi accretion rate nor Eddington accretion rate,why does this happen?
TNG assumes a Bondi accretion model, so the accretion rate is always equal to the Bondi rate (limited to a maximum value of the Eddington rate).
It seems to be the case for the majority of them, but there are still some black holes whose accretion rates are not equal to the Bondi rate or Eddington rate.The Fig1 shows part of this situation,and you can try
il.snapshot.loadSubhalo('./sims.TNG/TNG100-1/output/',99,32,5,['BH_Mdot','BH_MdotBondi','BH_MdotEddington'])
for example(whose results shown in Fig2,here accretion rate=0.00136819,Bondi rate=0.0063076,Eddington rate=0.17454475)
There are a few extra complications of the model, beyond Bondi. This is true, and often we overlook them.
In this case, I believe the difference will be the "external gas pressure" criterion, described in Vogelsberger+13 (Eqn. 23 and surrounding discussion).