.. _physics-blackHoleSeeds:

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``

.. _physics-blackHoleSeedsFixed:

``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]`` (real; 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]`` (real; 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.

.. _physics-blackHoleSeedsVergara2023:

``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 :cite:t:`vergara_global_2023` and :cite:t:`escala_observational_2021`.

**Parameters**

* ``[massSingleStar]`` (real; default ``1.0d0``) — Specifies the typical mass of a single star (in Solar masses) used in the :cite:t:`vergara_global_2023` stellar cluster collapse model for computing the black hole seed mass from a dense star cluster.
* ``[radiusSingleStar]`` (real; default ``1.0d0``) — Specifies the typical radius of a single star (in Solar radii) used in the :cite:t:`vergara_global_2023` stellar cluster collapse model for determining the cross-sections relevant to the seed formation process.
* ``[massEfficiency]`` (real; default ``1.0d-1``) — Specifies the efficiency of the mass converted into a black hole seed.
* ``[radiusEfficiency]`` (real; default ``1.0d0``) — Specifies the efficiency of the radius used to compute the critical mass.
* ``[massThreshold]`` (real; default ``1.0d3``) — Specifies the minimum stellar mass to apply the seeding prescription.