.. _physics-mergerTreeMassResolution: Merger Tree Building Mass Resolutions ===================================== Class providing the minimum progenitor halo mass (mass resolution) to resolve when building a merger tree. Branches below this mass are not followed individually; instead their accreted mass is treated as smooth, unresolved accretion onto the main progenitor. The mass resolution controls the trade-off between completeness of the merger history and computational cost, and can be set as a fixed value, a fraction of the root halo mass, or adaptively based on tree size. **Default implementation:** ``mergerTreeMassResolutionFixed`` Methods ------- ``resolution`` → ``double precision`` Gives the mass resolution to use for the given tree. * ``type(mergerTree), intent(in ) :: tree`` .. _physics-mergerTreeMassResolutionFixed: ``mergerTreeMassResolutionFixed`` --------------------------------- A merger tree mass resolution class which assumes a fixed, uniform mass resolution applied to all merger trees during tree construction. The minimum resolved halo mass is set by the ``[massResolution]`` parameter, expressed in Solar masses, below which branches are not built. **(Default implementation)** **Parameters** * ``[mass]`` (default ``100.0d0``) — The fixed mass (in :math:`\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 :math:`-1` and :math:`+1`) assigned to all newly-formed seed black holes, where :math:`0` corresponds to a non-rotating Schwarzschild black hole and :math:`\pm 1` to a maximally rotating Kerr black hole. * ``[fraction]`` (default ``0.01d0``) — The fixed fraction :math:`f_\mathrm{outflow}` of the stellar energy input rate (normalized to a canonical :math:`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 :math:`\mathrm{M}_\odot \hbox{Gyr}^{-1}`. * ``[proposalSize]`` — The fixed value of the proposal scaling parameter :math:`\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 :math:`\alpha` by which the proposal size :math:`\gamma` is scaled as :math:`\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 :cite:t:`benson_orbital_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 :cite:t:`benson_orbital_2005`. * ``[rateCoefficient]`` — The rate coefficient (in units of cm\ :math:`^3` s\ :math:`^{-1}`) for radiative recombination. * ``[gamma]`` (default ``0.67d0``) — The multiplicative factor, :math:`\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 :math:`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 :term:`IGM`. * ``[factor]`` (default ``sqrt(0.5d0)``) — The ratio of galaxy radius to :math:`\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 :math:`\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 :math:`\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 :math:`\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. .. _physics-mergerTreeMassResolutionScaled: ``mergerTreeMassResolutionScaled`` ---------------------------------- A merger tree mass resolution class which computes the mass resolution to be min(``[massResolutionMaximum]``,max(``[massResolutionMinimum]``,\ ``[massResolutionFractional]``\ :math:`\times M_\mathrm{base}`)), where :math:`M_\mathrm{base}` is the base mass of the merger tree. **Parameters** * ``[massResolutionMinimum]`` (default ``5.0d9``) — The minimum mass resolution to use when building merger trees. * ``[massResolutionMaximum]`` (default ``huge(0.0d0)``) — The maximum mass resolution to use when building merger trees. * ``[massResolutionFractional]`` (default ``1.0d-3``) — The fraction of the tree's root node mass to be used for the mass resolution when building merger trees. * ``[scale]`` (default ``1.0d0``) — The multiplicative factor applied to the rms mass variance :math:`\sigma(M,t)` returned by the wrapped :galacticus-class:`cosmologicalMassVarianceClass` object, allowing renormalization of the power spectrum amplitude.