.. _physics-hotHaloRamPressureTimescale:

Hot Halo Ram Pressure Timescales
================================

Class providing models of the ram pressure stripping timescale (in Gyr) for the hot gas atmosphere of a satellite galaxy orbiting in its host halo. Instead of computing an instantaneous stripping radius, the timescale approach allows for gradual stripping of hot gas over time, capturing the orbital history and the time required for ram pressure to overcome the satellite's self-gravity. The timescale may depend on the local ram pressure, the orbital velocity, or the halo dynamical time.

**Default implementation:** ``hotHaloRamPressureTimescaleRamPressureAcceleration``

Methods
-------

``timescale`` → ``double precision``
   Return the ram pressure stripping timescale for ``node`` (in units of Gyr).

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

.. _physics-hotHaloRamPressureTimescaleHaloDynamicalTime:

``hotHaloRamPressureTimescaleHaloDynamicalTime``
------------------------------------------------

A hot halo ram pressure timescale class in which the timescale is equal to the halo dynamical time of the associated halo.

**Parameters**

* ``[multiplier]`` (default ``5.0d0``) — Specifies the rate at which reheated mass is returned to the hot phase in units of the inverse halo dynamical timed.

.. _physics-hotHaloRamPressureTimescaleRamPressureAcceleration:

``hotHaloRamPressureTimescaleRamPressureAcceleration``
------------------------------------------------------

A hot halo ram pressure timescale class which computes the ram pressure stripping timescale from the acceleration imparted by the ram pressure force. Following :cite:t:`roediger_ram_2007` this is approximated as:

.. math::

   a_\mathrm{ram pressure} = P_\mathrm{ram pressure}/\Sigma,

where :math:`P_\mathrm{ram pressure}` is the ram pressure force per unit area, and :math:`\Sigma` is the surface density of gas. The associated timescale to accelerate gas over a distance :math:`r_\mathrm{outer}` (the current outer radius of the hot halo) is then:

.. math::

   \tau_\mathrm{ram pressure} = \sqrt{2 r_\mathrm{outer} \Sigma_\mathrm{outer} / P_\mathrm{ram pressure}}.

**(Default implementation)**