Black Hole Seeds

Class providing models of the initial seed masses for supermassive black holes and their formation channel. Black hole seeds are the initial conditions for black hole growth via accretion and mergers, and their masses and formation channels (e.g. stellar collapse, direct collapse, star cluster collapse) are set when a new black hole component is initialized in a halo.

Default implementation: blackHoleSeedsFixed

Methods

mass → double precision

Computes the mass of the black hole seed in the given node.

  • type(treeNode), intent(inout) :: node

spin → double precision

Computes the spin of the black hole seed in the given node.

  • type(treeNode), intent(inout) :: node

formationChannel → type(enumerationBlackHoleFormationChannelType)

Returns the formation channel of the seed in the given node.

  • type(treeNode), intent(inout) :: node

blackHoleSeedsFixed

A model of black hole seeds in which seeds have fixed mass and spin, independent of the halo in which they form.

(Default implementation)

Parameters

  • [mass] (default 100.0d0) — The fixed mass (in \(\mathrm{M}_\odot\)) assigned to all newly-formed seed black holes in this implementation, representing the initial black hole mass when a halo first forms a central black hole.

  • [spin] (default 0.0d0) — The dimensionless spin parameter (between \(-1\) and \(+1\)) assigned to all newly-formed seed black holes, where \(0\) corresponds to a non-rotating Schwarzschild black hole and \(\pm 1\) to a maximally rotating Kerr black hole.

  • [fraction] (default 0.01d0) — The fixed fraction \(f_\mathrm{outflow}\) of the stellar energy input rate (normalized to a canonical \(1\,\mathrm{M}_\odot\) population) that drives gas outflows, setting the mass loading factor for stellar feedback in the galaxy.

  • [escapeFraction] (default 0.006d0) — Escape fraction of ionizing photons from young HII regions.

  • [ageLimit] (default 0.03d0) — The age beyond which all ionizing photons are assumed to escape from HII regions.

  • [timescale] (default 1.0d0) — The timescale for star formation in the fixed timescale model.

  • [rateStarFormation] (default 1.0d9) — The rate of star formation in units of \(\mathrm{M}_\odot \hbox{Gyr}^{-1}\).

  • [proposalSize] — The fixed value of the proposal scaling parameter \(\gamma\) used to scale the vector difference between two randomly selected chain states when forming differential evolution proposals.

  • [exponentValue] — The fixed value of the temperature-scaling exponent \(\alpha\) by which the proposal size \(\gamma\) is scaled as \(\gamma \propto T^{\alpha}\) in tempered differential evolution runs.

  • [massResolution] (default 5.0d9) — The mass resolution to use when building merger trees.

  • [rootVariance] — The root variance of the random error distribution.

  • [velocityRadial] (default -0.90d0) — The radial velocity (in units of the host virial velocity) to used for the fixed virial orbits distribution. Default value matches approximate peak in the distribution of Benson (2005).

  • [velocityTangential] (default 0.75d0) — The tangential velocity (in units of the host virial velocity) to used for the fixed virial orbits distribution. Default value matches approximate peak in the distribution of Benson (2005).

  • [rateCoefficient] — The rate coefficient (in units of cm\(^3\) s\(^{-1}\)) for radiative recombination.

  • [gamma] (default 0.67d0) — The multiplicative factor, \(\gamma\), used to compute the cooling coefficient.

  • [fractionLossAngularMomentum] (default 0.3d0) — Specifies the fraction of angular momentum that is lost from cooling/infalling gas.

  • [concentration] — The fixed NFW concentration parameter \(c = r_\mathrm{virial}/r_\mathrm{scale}\) assigned to all halos regardless of mass or redshift, representing the ratio of the virial radius to the scale radius of the dark matter density profile.

  • [metallicity] — The metallicity (relative to Solar) of the IGM.

  • [factor] (default sqrt(0.5d0)) — The ratio of galaxy radius to \(\lambda r_\mathrm{vir}\) in the “fixed” galactic structure radius solver algorithm. This will be applied to any component for which no component-specific value is provided.

  • [factorDisk] (default sqrt(0.5d0)) — The ratio of galaxy radius to \(\lambda r_\mathrm{vir}\) in the “fixed” galactic structure radius solver algorithm for disks. This will override the generic value supplied by [factor] for disks.

  • [factorSpheroid] (default sqrt(0.5d0)) — The ratio of galaxy radius to \(\lambda r_\mathrm{vir}\) in the “fixed” galactic structure radius solver algorithm for spheroids. This will override the generic value supplied by [factor] for spheroids.

  • [radiusFixed] (default var_str('virial')) — The radius to use in the “fixed” galactic structure radius solver algorithm. Allowed options are “virial” and “turnaround”.

  • [overdensity] — The fixed linear overdensity \(\delta\) of the large-scale environment assigned uniformly to all halos; a positive value places halos in an overdense region, while negative values simulate voids.

  • [radiusEnvironment] (default 0.0d0) — The radius of the sphere used to determine the variance in the environmental density.

  • [massEnvironment] (default 1.0d15) — The mass within the sphere sphere used to determine the variance in the environmental density.

  • [densityContrastValue] (default 200.0d0) — The virial density contrast to use in the fixed value model.

  • [densityType] (default var_str('critical')) — The reference density to use in the fixed value virial density contrast model. Either of critical and mean are allowed.

  • [turnAroundOverVirialRadius] (default 2.0d0) — The ratio of the turnaround to virial radii in the fixed value model.

  • [criticalOverdensity] (default (3.0d0/20.0d0)*(12.0d0*Pi)**(2.0d0/3.0d0)) — The value to use for the critical overdensity for collapse of dark matter halos when using a fixed value.

blackHoleSeedsVergara2023

A model of black hole seeds in which seeds are formed due to the collapse of nuclear star clusters into a black hole, based on the model of Vergara et al. (2023) and Escala (2021).

Parameters

  • [massSingleStar] (default 1.0d0) — Specifies the typical mass of a single star (in Solar masses) used in the Vergara et al. (2023) stellar cluster collapse model for computing the black hole seed mass from a dense star cluster.

  • [radiusSingleStar] (default 1.0d0) — Specifies the typical radius of a single star (in Solar radii) used in the Vergara et al. (2023) stellar cluster collapse model for determining the cross-sections relevant to the seed formation process.

  • [massEfficiency] (default 1.0d-1) — Specifies the efficiency of the mass converted into a black hole seed.

  • [radiusEfficiency] (default 1.0d0) — Specifies the efficiency of the radius used to compute the critical mass.

  • [massThreshold] (default 1.0d3) — Specifies the minimum stellar mass to apply the seeding prescription.