.. _physics-stellarPopulationProperties:

Stellar Population Properties
=============================

Class providing stellar population properties---essentially the rates of change of stellar and gas mass and abundances given a star formation rate and fuel abundances (and perhaps a historical record of star formation in the component).

**Default implementation:** ``stellarPopulationPropertiesInstantaneous``

Methods
-------

``rates`` → ``void``
   Returns the rates of change of stellar population properties (stellar mass, fuel mass, elemental abundances, luminosities, and energy input) for a given star formation rate and fuel abundances, using either instantaneous recycling or a full stellar population model.

   * ``double precision , intent(in ) :: rateStarFormation``

   * ``type (abundances ), intent(in ) :: abundancesFuel``

   * ``class (nodeComponent ), intent(in ) :: component``

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

   * ``type (history ), intent(inout) :: history_``

   * ``double precision , intent( out) :: rateMassStellar , rateMassFuel , rateEnergyInput``

   * ``type (abundances ), intent(inout) :: rateAbundancesFuel , rateAbundancesStellar``

   * ``type (stellarLuminosities), intent(inout) :: rateLuminosityStellar``

   * ``logical , intent(in ) :: computeRateLuminosityStellar``

``scales`` → ``void``
   Return scaling factors of stellar population properties for an :term:`ODE` solver.

   * ``double precision , intent(in ) :: massStellar``

   * ``type (abundances), intent(in ) :: abundancesStellar``

   * ``type (history ), intent(inout) :: history_``

``historyCount`` → ``integer``
   Return the number of stellar population property histories which must be stored.

``historyCreate`` → ``void``
   Create histories needed to store stellar population properties.

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

   * ``type(history ), intent(inout) :: history_``

.. _physics-stellarPopulationPropertiesInstantaneous:

``stellarPopulationPropertiesInstantaneous``
--------------------------------------------

A stellar population properties class based on the instantaneous recycling approximation. Specifically, given a star formation rate :math:`\phi`, this method assumes a rate of increase of stellar mass of :math:`\dot{M}_\star=(1-R)\phi`, a corresponding rate of decrease in fuel mass. The rate of change of the metal content of stars follows from the fuel metallicity, while that of the fuel changes according to

.. math::

   \dot{M}_{fuel,Z} = - (1-R) Z_\mathrm{fuel} \phi + p \phi.

In the above :math:`R` is the instantaneous recycled fraction and :math:`p` is the yield, both of which are supplied by the :term:`IMF` subsystem. The rate of energy input from the stellar population is computed assuming that the canonical amount of energy from a single stellar population (as defined by the ``feedbackEnergyInputAtInfinityCanonical``) is input instantaneously.

**(Default implementation)**

.. _physics-stellarPopulationPropertiesNoninstantaneous:

``stellarPopulationPropertiesNoninstantaneous``
-----------------------------------------------

A stellar population properties class based on the noninstantaneous recycling approximation---fully non-instantaneous recycling and metal enrichment are used. Recycling and metal production rates from simple stellar populations are computed, for any given :term:`IMF`, from stellar evolution models. The rates of change are then:

.. math::

   \dot{M}_\star & = \phi - \int_0^t \phi(t^\prime) \dot{R}(t-t^\prime;Z_\mathrm{fuel}[t^\prime]) \d t^\prime, \\
   \dot{M}_\mathrm{fuel} & = -\phi + \int_0^t \phi(t^\prime) \dot{R}(t-t^\prime;Z_\mathrm{fuel}[t]) \d t^\prime, \\
   \dot{M}_{\star,Z} & = Z_\mathrm{fuel} \phi - \int_0^t \phi(t^\prime) Z_\mathrm{fuel}(t^\prime)
   \dot{R}(t-t^\prime;Z_\mathrm{fuel}[t^\prime]) \d t^\prime, \\
   \dot{M}_{\mathrm{fuel},Z} & = -Z_\mathrm{fuel} \phi + \int_0^t \phi(t^\prime) \{ Z_\mathrm{fuel}(t^\prime)
   \dot{R}(t-t^\prime;Z_\mathrm{fuel}[t^\prime]) + \dot{p}(t-t^\prime;Z_\mathrm{fuel}[t^\prime]) \} \d t^\prime, \\

where :math:`\dot{R}(t;Z)` and :math:`\dot{p}(t;Z)` are the recycling and metal yield rates respectively from a stellar population of age :math:`t` and metallicity :math:`Z`. The energy input rate is computed self-consistently from the star formation history.

**Parameters**

* ``[countHistoryTimes]`` (default ``10``) — The number of times at which a galaxy's stellar properties history is stored.