Massive Black Hole Physics Parameters¶
Following parameters are for the accretion and feedback from the
massive black hole particle (PARTICLE_TYPE_MBH
). Details
are described in Kim, Wise, Alvarez, and Abel (2011).
Accretion Physics¶
MBHAccretion
(external)- Set to 1 to turn on accretion based on the Eddington-limited
spherical Bondi-Hoyle formula (Bondi 1952). Set to 2 to turn on
accretion based on the Bondi-Hoyle formula but with fixed
temperature defined below. Set to 3 to turn on accretion with a
fixed rate defined below. Set to 4 to to turn on accretion based on
the Eddington-limited spherical Bondi-Hoyle formula, but without
v_rel in the denominator. Set to 5 to turn on accretion based on
Krumholz et al.(2006) which takes vorticity into account. Set to 6
to turn on alpha disk formalism based on DeBuhr et al.(2010).
7 and 8 are still failed experiment. Add 10 to each of these options
(i.e. 11, 12, 13, 14) to ignore the Eddington limit. See
Star_CalculateMassAccretion.C
. Default: 0 (FALSE) MBHAccretionRadius
(external)- This is the radius (in pc) of a gas sphere from which the accreting
mass is subtracted out at every timestep. Instead, you may want to
try set this parameter to -1, in which case an approximate Bondi
radius is calculated and used (from
DEFAULT_MU
andMBHAccretionFixedTemperature
). If set to -N, it will use N*(Bondi radius). SeeCalculateSubtractionParameters.C
. Default: 50.0 MBHAccretingMassRatio
(external)- There are three different scenarios you can utilize this parameter.
(1) In principle this parameter is a nondimensional factor
multiplied to the Bondi-Hoyle accretion rate; so 1.0 should give
the plain Bondi rate. (2) However, if the Bondi radius is resolved
around the MBH, the local density used to calculate Mdot can be
higher than what was supposed to be used (density at the Bondi
radius!), resulting in the overestimation of Mdot. 0.0 <
MBHAccretingMassRatio
< 1.0 can be used to fix this. (3) Or, one might try using the density profile of R-1.5 to estimate the density at the Bondi radius, which is utilized whenMBHAccretingMassRatio
is set to -1. SeeStar_CalculateMassAccretion.C
. Default: 1.0 MBHAccretionFixedTemperature
(external)- This parameter (in K) is used when
MBHAccretion = 2
. A fixed gas temperature that goes into the Bondi-Hoyle accretion rate estimation formula. Default: 3e5 MBHAccretionFixedRate
(external)- This parameter (in Msun/yr) is used when
MBHAccretion = 3
. Default: 1e-3 MBHTurnOffStarFormation
(external)- Set to 1 to turn off star formation (only for
StarParicleCreation
method 7) in the cells where MBH particles reside. Default: 0 (FALSE) MBHCombineRadius
(external)- The distance (in pc) between two MBH particles in which two energetically-bound MBH particles merge to form one particle. Default: 50.0
MBHMinDynamicalTime
(external)- Minimum dynamical time (in yr) for a MBH particle. Default: 1e7
MBHMinimumMass
(external)- Minimum mass (in Msun) for a MBH particle. Default: 1e3
Feedback Physics¶
MBHFeedback
(external)- Set to 1 to turn on thermal feedback of MBH particles (
MBH_THERMAL
- not fully tested). Set to 2 to turn on mechanical feedback of MBH particles (MBH_JETS
, bipolar jets along the total angular momentum of gas accreted onto the MBH particle so far). Set to 3 to turn on another version of mechanical feedback of MBH particles (MBH_JETS
, always directed along z-axis). Set to 4 to turn on experimental version of mechanical feedback (MBH_JETS, bipolar jets along the total angular momentum of gas accreted onto the MBH particle so far + 10 degree random noise). Set to 5 to turn on experimental version of mechanical feedback (MBH_JETS
, launched at random direction). Note that, even when this parameter is set to 0, MBH particles still can be radiation sources ifRadiativeTransfer
is on. SeeGrid_AddFeedbackSphere.C
. Default: 0 (FALSE)``RadiativeTransfer = 0`` & ``MBHFeedback = 0`` : no feedback at all ``RadiativeTransfer = 0`` & ``MBHFeedback = 1`` : purely thermal feedback ``RadiativeTransfer = 0`` & ``MBHFeedback = 2`` : purely mechanical feedback ``RadiativeTransfer = 1`` & ``MBHFeedback = 0`` : purely radiative feedback ``RadiativeTransfer = 1`` & ``MBHFeedback = 2`` : radiative and mechanical feedback combined (one has to change the following ``MBHFeedbackRadiativeEfficiency`` parameter accordingly, say from 0.1 to 0.05, to keep the same total energy across different modes of feedback)
MBHFeedbackRadiativeEfficiency
(external)- The radiative efficiency of a black hole. 10% is the widely accepted value for the conversion rate from the rest-mass energy of the accreting material to the feedback energy, at the innermost stable orbit of a non-spinning Schwarzschild black hole (Shakura & Sunyaev 1973, Booth & Schaye 2009). Default: 0.1
MBHFeedbackEnergyCoupling
(external)- The fraction of feedback energy that is thermodynamically (for
MBH_THERMAL
) or mechanically (forMBH_JETS
) coupled to the gas. 0.05 is widely used for thermal feedback (Springel et al. 2005, Di Matteo et al. 2005), whereas 0.0001 or less is recommended for mechanical feedback depending on the resolution of the simulation (Ciotti et al. 2009). Default: 0.05 MBHFeedbackMassEjectionFraction
(external)- The fraction of accreting mass that is returning to the gas phase.
For either
MBH_THERMAL
orMBH_JETS
. Default: 0.1 MBHFeedbackMetalYield
(external)- The mass fraction of metal in the ejected mass. Default: 0.02
MBHFeedbackThermalRadius
(external)- The radius (in pc) of a sphere in which the energy from
MBH_THERMAL
feedback is deposited. If set to a negative value, the radius of a sphere gets bigger in a way that the sphere encloses the constant mass (= 4/3*pi*(-MBHFeedbackThermalRadius
)3 Msun). The latter is at the moment very experimental; seeStar_FindFeedbackSphere.C
. Default: 50.0 MBHFeedbackJetsThresholdMass
(external)- The bipolar jets by
MBH_JETS
feedback are injected every time the accumulated ejecta mass surpassesMBHFeedbackJetsThresholdMass
(in Msun). Although continuously injecting jets into the gas cells might sound great, unless the gas cells around the MBH are resolved down to Mdot, the jets make little or no dynamical impact on the surrounding gas. By imposingMBHFeedbackJetsThresholdMass
, the jets from MBH particles are rendered intermittent, yet dynamically important. Default: 10.0 MBHParticleIO
(external)- Set to 1 to print out basic information about MBH particles. Will
be automatically turned on if
MBHFeedback
is set to 2 or 3. Default: 0 (FALSE) MBHParticleIOFilename
(external)- The name of the file used for the parameter above. Default:
mbh_particle_io.dat