.. _physics-coldModeInfallRate:

Cold Mode Accretion Infall Rates
================================

Class providing models of the cold-mode infall rate (in :math:`\mathrm{M}_\odot` Gyr\ :math:`^{-1}`) at which gas streams along cold filaments directly into the galaxy, bypassing the hot atmosphere. Cold-mode accretion is thought to dominate at high redshift and in lower-mass halos where the virial temperature is too low to maintain a stable hot atmosphere. The cold-mode infall rate supplements the hot-mode cooling rate to give the total gas supply available for star formation.

**Default implementation:** ``coldModeInfallRateDynamicalTime``

Methods
-------

``infallRate`` → ``double precision``
   Returns the cold mode infall rate for ``node`` (in units of :math:`\mathrm{M}_\odot` Gyr\ :math:`^{-1}`).

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

.. _physics-coldModeInfallRateDynamicalTime:

``coldModeInfallRateDynamicalTime``
-----------------------------------

A cold mode infall rate class in which the infall rate from the cold mode is given by

.. math::

   \dot{M}_\mathrm{infall, cold mode} = f_\mathrm{infall, cold mode}{M_\mathrm{cold mode} \over \tau_\mathrm{dyn}},

where :math:`f_\mathrm{infall, cold mode}=`\ ``[dynamicalRateFraction]``.

**(Default implementation)**

**Parameters**

* ``[efficiency]`` (default ``0.01d0``) — The efficiency of star formation for the dynamical time method.
* ``[exponentVelocity]`` (default ``-1.50d0``) — The velocity exponent for star formation for the dynamical time method.
* ``[timescaleMinimum]`` (default ``1.0d-3``) — The minimum allowed timescale for star formation (in Gyr) in the dynamical time prescription, preventing unphysically short formation timescales in high-density or high-velocity systems.
* ``[dynamicalRateFraction]`` (default ``2.0d0``) — The fraction of the inverse dynamical time to use as the rate for infall of the cold mode component.