.. _physics-darkMatterHaloMassLossRate:

Dark Matter Halo Mass Loss Rates
================================

Class providing models of the rate of mass loss from dark matter (sub)halos due to tidal stripping and other processes. Returns the rate of change of halo mass (in :math:`\mathrm{M}_\odot` Gyr\ :math:`^{-1}`) for a given node. This class is used in combination with tidal stripping models to track the evolution of subhalo masses as they orbit within a host halo.

**Default implementation:** ``darkMatterHaloMassLossRateZero``

Methods
-------

``rate`` → ``double precision``
   Returns the rate of mass loss (in :math:`\mathrm{M}_\odot`/Gyr) from ``node``.

   * ``type(treeNode), intent(inout) :: node``

.. _physics-darkMatterHaloMassLossRateVanDenBosch:

``darkMatterHaloMassLossRateVanDenBosch``
-----------------------------------------

A dark matter halo mass loss rate class which uses the algorithm of :cite:t:`van_den_bosch_mass_2005` to compute the rate of mass loss. Specifically:

.. math::

   \dot{M}_\mathrm{node,bound} = -{M_\mathrm{node,bound}\over \tau} \left({M_\mathrm{node,bound} / M_\mathrm{node,parent}}\right)^\zeta,

where :math:`M_\mathrm{node,parent}` is the mass of the parent :term:`node` in which the halo lives and

.. math::

   \tau = \tau_0 \left({\Delta_\mathrm{vir}(t) \over \Delta(t_0)}\right)^{-1/2} a^{3/2},

where :math:`\Delta_\mathrm{vir}(t)` is the virial overdensity of halos at time :math:`t` and :math:`a` is the expansion factor. The fitting parameters, :math:`\tau_0` and :math:`\zeta` have values of 0.13 Gyr and 0.36 respectively as determined by :cite:t:`van_den_bosch_mass_2005`. Note that :cite:t:`van_den_bosch_mass_2005` write this expression in a slightly different form since their :math:`\Delta_\mathrm{vir}` is defined relative to the critical density rather than the mean density as it is in Galacticus. In both cases, the timescale :math:`\tau` simply scales as :math:`\langle \rho_\mathrm{vir} \rangle ^{-1/2}` where :math:`\langle \rho_\mathrm{vir} \rangle` is the mean virial overdensity of halos.

**Parameters**

* ``[timescaleNormalization]`` (default ``0.13d0``) — The mass loss timescale normalization (in Gyr) for the :cite:t:`van_den_bosch_mass_2005` dark matter halo mass loss rate algorithm.
* ``[zeta]`` (default ``0.36d0``) — The mass loss scaling with halo mass for the :cite:t:`van_den_bosch_mass_2005` dark matter halo mass loss rate algorithm.

.. _physics-darkMatterHaloMassLossRateZero:

``darkMatterHaloMassLossRateZero``
----------------------------------

A dark matter halo mass loss rate class which assumes a zero rate of mass loss from dark matter halos.

**(Default implementation)**