.. _physics-ramPressureStripping:

Ram Pressure Stripping
======================

Class providing models of ram pressure stripping-induced rates of mass loss---the removal of cold interstellar gas from satellite galaxies as they move through the hot intracluster or intragroup medium of their host halo. The ram pressure :math:`P_\mathrm{ram} = \rho_\mathrm{ICM} v^2` exerted by the ambient gas on the disc component strips cold gas at a rate (in :math:`\mathrm{M}_\odot` Gyr\ :math:`^{-1}`) that depends on the satellite velocity, the host gas density at the satellite's position, and the restoring pressure from the disc's self-gravity. This process quenches star formation in satellite galaxies on short timescales.

**Default implementation:** ``ramPressureStrippingSimpleCylindrical``

Methods
-------

``rateMassLoss`` → ``double precision``
   Returns the rate of mass loss (in :math:`\mathrm{M}_\odot` Gyr\ :math:`^{-1}`) due to ram pressure stripping of the given ``component``.

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

.. _physics-ramPressureStrippingSimpleCylindrical:

``ramPressureStrippingSimpleCylindrical``
-----------------------------------------

A ram pressure stripping class which applies to systems with cylindrical symmetry (e.g. disks), and computes the mass loss rate to be:

.. math::

   \dot{M}_\mathrm{gas, disk} = \hbox{min}\left({\beta \mathcal{F}_\mathrm{hot, host} \over 2 \pi \mathrm{G}
   \Sigma_\mathrm{gas}(r_\mathrm{half}) \Sigma_\mathrm{total}(r_\mathrm{half})}, R_\mathrm{maximum}\right) {M_\mathrm{gas,
   disk} \over \tau_\mathrm{dyn, disk}},

where :math:`\mathcal{F}_\mathrm{hot, host}` is the ram pressure force due to the hot halo of the node's host (computed using the selected hot halo ram pressure force method; see :galacticus-class:`hotHaloRamPressureForce`), :math:`\Sigma_\mathrm{gas}(r)` is the gas surface density in the disk, :math:`\Sigma_\mathrm{total}(r)` is the total surface density in the disk, :math:`r_\mathrm{half}` is the disk half-mass radius, :math:`M_\mathrm{gas, disk}` is the total gas mass in the disk, :math:`\tau_\mathrm{dyn, disk} = r_\mathrm{disk}/v_\mathrm{disk}` is the dynamical time in the disk, :math:`\beta=`\ ``[beta]`` scales the rate of mass loss, and :math:`R_\mathrm{maximum}=`\ ``[rateFractionalMaximum]`` controls the maximum allowed rate of mass loss.

**(Default implementation)**

**Parameters**

* ``[rateFractionalMaximum]`` (default ``10.0d0``) — The maximum fractional mass loss rate per dynamical time in the simple model of mass loss in cylindrically symmetric systems due to ram pressure stripping.
* ``[beta]`` (default ``1.0d0``) — The scaling factor which multiplies the ram pressure mass loss rate.

.. _physics-ramPressureStrippingSimpleSpherical:

``ramPressureStrippingSimpleSpherical``
---------------------------------------

A simple model of ram pressure stripping in spherically-symmetric systems (e.g. spheroids). The mass loss rate is given by:

.. math::

   \dot{M}_\mathrm{gas} = -\hbox{max}(\alpha,R_\mathrm{maximum}) M_\mathrm{gas}/\tau_\mathrm{spheroid},

where :math:`R_\mathrm{maximum}=`\ ``[ramPressureStrippingMassLossRateSpheroidSimpleFractionalRateMax]``

.. math::

   \alpha = \beta \mathcal{F}_\mathrm{hot,host}/F_\mathrm{gravity},

and,

.. math::

   F_\mathrm{gravity} = {4\over 3} \rho_\mathrm{gas}(r_{1/2}) {\mathrm{G} M_\mathrm{total}(r_{1/2})\over r_{1/2}}

is the gravitational restoring force in the spheroid at the half-mass radius, :math:`r_\mathrm{1/2}` :cite:p:`takeda_ram_1984`, :math:`\beta=`\ ``[beta]`` scales the rate of mass loss, and :math:`R_\mathrm{maximum}=`\ ``[rateFractionalMaximum]`` controls the maximum allowed rate of mass loss.

**Parameters**

* ``[rateFractionalMaximum]`` (default ``10.0d0``) — The maximum fractional mass loss rate per dynamical time in the simple model of mass loss from spherically-symmetric due to ram pressure stripping.
* ``[beta]`` (default ``1.0d0``) — The scaling factor which multiplies the ram pressure mass loss rate.