.. _physics-mergerMassMovements: Merger Mass Movements ===================== Class providing models of the movements of mass during galaxy mergers---the prescription for where the gas and stellar components of the satellite and host galaxies are redistributed after a merger event. Implementations specify the destination (disc, spheroid, or dominant component) for the gas and stars of both the satellite and the host, and whether the merger should be classified as major or minor. This drives the morphological transformation of merging galaxies, controlling bulge growth and triggering starbursts during coalescence. **Default implementation:** ``mergerMassMovementsSimple`` Methods ------- ``get`` → ``void`` Determine the movements of stellar and gaseous mass components during a galaxy merger event, returning the destination (disk, spheroid, or dominant component) for each component of the satellite and host galaxies, and whether the merger should be classified as major or minor. * ``type (treeNode ), intent(inout), target :: node`` * ``type (enumerationDestinationMergerType), intent( out) :: destinationGasSatellite, destinationStarsSatellite, destinationGasHost, destinationStarsHost`` * ``logical , intent( out) :: mergerIsMajor`` .. _physics-mergerMassMovementsBaugh2005: ``mergerMassMovementsBaugh2005`` -------------------------------- A merger mass movements class which implements mass movements according to: * If :math:`M_\mathrm{satellite} > f_\mathrm{major} M_\mathrm{central}` then all mass from both satellite and central galaxies moves to the spheroid :term:`component` of the central galaxy; * Otherwise: * If :math:`M_\mathrm{central, spheroid} < f_\mathrm{burst} M_\mathrm{central}` and the gas fraction in the host equals or exceeds :math:`f_\mathrm{gas,crit}` then all gas is moved to the host spheroid, while the host stellar disk remains in place. * Otherwise, gas from the satellite moves to the :term:`component` of the central specified by the ``[destinationGasMinorMerger]`` parameter (either "``disk``" or "``spheroid``"), stars from the satellite moves to the spheroid of the central and mass in the central does not move. Here, :math:`f_\mathrm{major}=`\ ``[massRatioMajorMerger]`` is the mass ratio above which a merger is considered to be "major", while :math:`f_\mathrm{burst}=`\ ``[ratioMassBurst]`` and :math:`f_\mathrm{gas,crit}=`\ ``[fractionGasCriticalBurst]``. **Parameters** * ``[timescale]`` (default ``8.0d0``) — The timescale (in Gyr) for star formation in the :cite:t:`baugh_can_2005` prescription. * ``[exponentVelocity]`` (default ``-3.0d0``) — The exponent for velocity in the :cite:t:`baugh_can_2005` prescription for star formation. * ``[exponentExpansionFactor]`` (default ``0.0d0``) — The exponent for expansion factor in the :cite:t:`baugh_can_2005` prescription for star formation. * ``[velocityNormalization]`` (default ``200.0d0``) — The normalization velocity :math:`V_0` (in km/s) appearing in the :cite:t:`baugh_can_2005` star formation timescale relation :math:`\tau_\star = \tau_0 (V_\mathrm{disk}/V_0)^\alpha a^\beta`. * ``[massRatioMajorMerger]`` (default ``0.25d0``) — The mass ratio above which mergers are considered to be "major". * ``[ratioMassBurst]`` (default ``0.05d0``) — The mass ratio above which mergers are considered to trigger a burst. * ``[fractionGasCriticalBurst]`` (default ``0.75d0``) — The host gas fraction above which mergers are considered to trigger a burst. * ``[destinationGasMinorMerger]`` (default ``var_str('spheroid')``) — The component to which satellite galaxy gas moves to as a result of a minor merger. .. _physics-mergerMassMovementsSimple: ``mergerMassMovementsSimple`` ----------------------------- A merger mass movements class which implements mass movements according to: * If :math:`M_\mathrm{satellite} > f_\mathrm{major} M_\mathrm{central}` then all mass from both satellite and central galaxies moves to the spheroid :term:`component` of the central galaxy; * Otherwise: Gas from the satellite moves to the :term:`component` of the central specified by the ``[minorMergerGasMovesTo]`` parameter (either "``disk``" or "``spheroid``"), stars from the satellite moves to the spheroid of the central and mass in the central does not move. Here, :math:`f_\mathrm{major}=`\ ``[majorMergerMassRatio]`` is the mass ratio above which a merger is considered to be "major". **(Default implementation)** **Methods** * ``calculationReset`` — Reset memoized calculations. **Parameters** * ``[efficiencyWind]`` (default ``2.2157d-3``) — The coupling efficiency of the black hole accretion-driven wind, defined as the fraction of the accreted rest-mass energy that is deposited as kinetic or thermal energy into the surrounding gas via AGN-driven outflows. * ``[redshiftReionization]`` (default ``9.97d0``) — The redshift of reionization below which baryonic accretion onto halos is suppressed due to the ionizing background heating the intergalactic medium and preventing gas from accreting onto low-mass halos. * ``[opticalDepthReionization]`` — The optical depth to electron scattering below which baryonic accretion is suppressed. * ``[velocitySuppressionReionization]`` (default ``35.0d0``) — The velocity scale below which baryonic accretion is suppressed. * ``[accretionNegativeAllowed]`` (default ``.true.``) — Specifies whether negative accretion (mass loss) is allowed in the simple halo accretion model. * ``[accretionNewGrowthOnly]`` (default ``.false.``) — Specifies whether accretion from the :term:`IGM` is allowed only when a halo is growing past its previous greatest mass. * ``[acceptedStateCount]`` (default ``100``) — The number of states to use in acceptance rate statistics. * ``[timeStepRelative]`` (default ``0.1d0``) — The maximum allowed relative change in time for a single step in the evolution of a node. * ``[timeStepAbsolute]`` (default ``1.0d0``) — The maximum allowed absolute change in time (in Gyr) for a single step in the evolution of a node. * ``[timeStepMinimum]`` (default ``1.0d-6``) — The smallest timestep to use in profiling ODE solver steps. * ``[timeStepMaximum]`` (default ``1.0d+1``) — The largest timestep to use in profiling ODE solver steps. * ``[timeStepPointsPerDecade]`` (default ``3``) — The number of bins per decade of timestep to use when profiling ODE solver steps. * ``[wavelength]`` (default ``1.0d4``) — The wavelength of the photon packet (in \AA). * ``[wavelengthMinimum]`` (default ``0.5d4``) — The minimum wavelength of the photon packet (in \AA). * ``[wavelengthMaximum]`` (default ``2.0d4``) — The maximum wavelength of the photon packet (in \AA). * ``[luminosity]`` (default ``1.0d0``) — The luminosity of the photon packet (in :math:`L_\odot`). * ``[massRatioMajorMerger]`` (default ``0.25d0``) — The mass ratio above which mergers are considered to be "major". * ``[destinationGasMinorMerger]`` (default ``var_str('spheroid')``) — The component to which satellite galaxy gas moves to as a result of a minor merger. * ``[destinationStarsMinorMerger]`` (default ``var_str('spheroid')``) — The component to which satellite galaxy stars move to as a result of a minor merger. * ``[degreesOfFreedom]`` (default ``3.0d0``) — Number of degrees of freedom to assume when computing the energy density of cooling gas in the "simple" cooling time class. * ``[timeScale]`` (default ``1.0d0``) — The timescale (in Gyr) for cooling in the simple cooling rate model. * ``[reionizationRedshift]`` (default ``9.97d0``) — The redshift of reionization in the simple :term:`IGM` state model. * ``[reionizationTemperature]`` (default ``1.0d4``) — The post-reionization temperature (in units of Kelvin) in the simple :term:`IGM` state model. * ``[preReionizationTemperature]`` (default ``10.0d0``) — The pre-reionization temperature (in units of Kelvin) in the simple :term:`IGM` state model. * ``[useFormationHalo]`` (default ``.false.``) — Specifies whether or not the "formation halo" should be used when solving for the radii of galaxies. * ``[solveForInactiveProperties]`` (default ``.true.``) — If true, galactic structure is solved for during evaluation of inactive property integrals. Otherwise, structure is not solved for during this phase---this should only be used if the inactive property integrands *do not* depend on galactic structure. * ``[rateFractionalMaximum]`` (default ``10.0d0``) — The maximum fractional mass loss rate per dynamical time in the simple model of mass loss due to tidal stripping. * ``[beta]`` (default ``1.0d0``) — The scaling factor which multiplies the tidal mass loss rate. * ``[OmegaMatter]`` (default ``0.3153d0``) — The density of matter in the Universe in units of the critical density. * ``[OmegaBaryon]`` (default ``0.04930d0``) — The density of baryons in the Universe in units of the critical density. * ``[OmegaDarkEnergy]`` (default ``0.6847d0``) — The density of dark energy in the Universe in units of the critical density. * ``[temperatureCMB]`` (default ``2.72548d0``) — The present day temperature of the :term:`CMB` in units of Kelvin. * ``[HubbleConstant]`` (default ``67.36d0``) — The present day value of the Hubble parameter in units of km/s/Mpc. .. _physics-mergerMassMovementsVerySimple: ``mergerMassMovementsVerySimple`` --------------------------------- A merger mass movements class which assumes that the satellite material is always added to the disk of the host, while the host mass is not moved. **Parameters** * ``[massRatioMajorMerger]`` (default ``0.25d0``) — The mass ratio above which mergers are considered to be "major".