.. _starparticleparameters: Star Formation and Feedback Parameters ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ For details on each of the different star formation methods available in Enzo see :ref:`star_particles`. General ^^^^^^^ ``StarParticleCreation`` (external) This parameter is bitwise so that multiple types of star formation routines can be used in a single simulation. For example if methods 1 and 3 are desired, the user would specify 10 (2\ :sup:`1`\ + 2\ :sup:`3`\ ), or if methods 1, 4 and 7 are wanted, this would be 146 (2\ :sup:`1`\ + 2\ :sup:`4`\ + 2\ :sup:`7`\ ). Default: 0 :: 0 - Cen & Ostriker (1992) 1 - Cen & Ostriker (1992) with stocastic star formation 2 - Global Schmidt Law / Kravstov et al. (2003) 3 - Population III stars / Abel, Wise & Bryan (2007) 4 - Sink particles: Pure sink particle or star particle with wind feedback depending on choice for HydroMethod / Wang et al. (2009) 5 - Radiative star clusters / Wise & Cen (2009) 6 - [reserved for future use] 7 - Cen & Ostriker (1992) with no delay in formation 8 - Springel & Hernquist (2003) 9 - Massive Black Hole (MBH) particles insertion by hand / Kim et al. (2010) 10 - Population III stellar tracers 11 - Molecular hydrogen regulated star formation ``StarParticleFeedback`` (external) This parameter works the same way as ``StarParticleCreation`` but only is valid for ``StarParticleCreation`` method = 0, 1, 2, 7 and 8 because methods 3, 5 and 9 use the radiation transport module and ``Star_*.C`` routines to calculate the feedback, 4 has explicit feedback and 10 does not use feedback. Default: 0. ``StarFeedbackDistRadius`` (external) If this parameter is greater than zero, stellar feedback will be deposited into the host cell and neighboring cells within this radius. This results in feedback being distributed to a cube with a side of ``StarFeedbackDistRadius+1``. It is in units of cell widths of the finest grid which hosts the star particle. Only implemented for ``StarParticleCreation`` method = 0 or 1 with ``StarParticleFeedback`` method = 1. (If ``StarParticleFeedback`` = 0, stellar feedback is only deposited into the cell in which the star particle lives). Default: 0. ``StarFeedbackDistCellStep`` (external) In essence, this parameter controls the shape of the volume where the feedback is applied, cropping the original cube. This volume that are within ``StarFeedbackDistCellSteps`` cells from the host cell, counted in steps in Cartesian directions, are injected with stellar feedback. Its maximum value is ``StarFeedbackDistRadius`` * ``TopGridRank``. Only implemented for ``StarParticleCreation`` method = 0 or 1 with ``StarParticleFeedback`` method = 1. See :ref:`distributed_feedback` for an illustration. Default: 0. ``StarMakerTypeIaSNe`` (external) This parameter turns on thermal and chemical feedback from Type Ia supernovae. The mass loss and luminosity of the supernovae are determined from `fits of K. Nagamine `_. The ejecta are traced in a separate species field, ``MetalSNIa_Density``. The metallicity of star particles that comes from this ejecta is stored in the particle attribute ``typeia_fraction``. Can be used with ``StarParticleCreation`` method = 0, 1, 2, 5, 7, and 8. Default: 0. ``StarMakerPlanetaryNebulae`` (external) This parameter turns on thermal and chemical feedback from planetary nebulae. The mass loss and luminosity are taken from the same `fits from K. Nagamine `_. The chemical feedback injects gas with the same metallicity as the star particle, and the thermal feedback equates to a 10 km/s wind. The ejecta are not stored in its own species field. Can be used with ``StarParticleCreation`` method = 0, 1, 2, 5, 7, and 8. Default: 0. Normal Star Formation ^^^^^^^^^^^^^^^^^^^^^ The parameters below are considered in ``StarParticleCreation`` method 0, 1, 2, 7 and 8. ``StarMakerOverDensityThreshold`` (external) The overdensity threshold in code units (for cosmological simulations, note that code units are relative to the total mean density, not just the dark matter mean density) before star formation will be considered. For ``StarParticleCreation`` method = 7 in cosmological simulations, however, ``StarMakerOverDensityThreshold`` should be in particles/cc, so it is not the ratio with respect to the ``DensityUnits`` (unlike most other star_makers). This way one correctly represents the Jeans collapse and molecular cloud scale physics even in cosmological simulations. Default: 100 ``StarMakerSHDensityThreshold`` (external) The critical density of gas used in Springel & Hernquist star formation ( \\rho_{th} in the paper) used to determine the star formation timescale in units of g cm\ :sup:`-3`\ . Only valid for ``StarParticleCreation`` method = 8. Default: 7e-26. ``StarMakerMassEfficiency`` (external) The fraction of identified baryonic mass in a cell (Mass\*dt/t_dyn) that is converted into a star particle. Default: 1 ``StarMakerMinimumMass`` (external) The minimum mass of star particle, in solar masses. Note however, the star maker algorithm 2 has a (default off) "stochastic" star formation algorithm that will, in a pseudo-random fashion, allow star formation even for very low star formation rates. It attempts to do so (relatively successfully according to tests) in a fashion that conserves the global average star formation rate. Default: 1e9 ``StarMakerMinimumDynamicalTime`` (external) When the star formation rate is computed, the rate is proportional to M_baryon \* dt/max(t_dyn, t_max) where t_max is this parameter. This effectively sets a limit on the rate of star formation based on the idea that stars have a non-negligible formation and life-time. The unit is years. Default: 1e6 ``StarMakerTimeIndependentFormation`` (external) When used, the factor of dt / t_dyn is removed from the calculation of the star particle mass above. Instead of the local dynamical time, the timescale over which feedback occurs is a constant set by the parameter ``StarMakerMinimumDynamicalTime``. This is necessary when running with conduction as the timesteps can be very short, which causes the calculated star particle mass to never exceed reasonable values for ``StarMakerMinimumMass``. This prevents cold, star-forming gas from actually forming stars, and when combined with conduction, results in too much heat being transferred out of hot gas. When running a cosmological simulation with conduction and star formation, one must use this otherwise bad things will happen. (1 - ON; 0 - OFF) Default: 0. ``StarMassEjectionFraction`` (external) The mass fraction of created stars which is returned to the gas phase. Default: 0.25 ``StarMetalYield`` (external) The mass fraction of metals produced by each unit mass of stars created (i.e. it is multiplied by mstar, not ejected). Default: 0.02 ``StarEnergyToThermalFeedback`` (external) The fraction of the rest-mass energy of the stars created which is returned to the gas phase as thermal energy. Default: 1e-5 ``StarEnergyToStellarUV`` (external) The fraction of the rest-mass energy of the stars created which is returned as UV radiation with a young star spectrum. This is used when calculating the radiation background. Default: 3e-6 ``StarEnergyToQuasarUV`` (external) The fraction of the rest-mass energy of the stars created which is returned as UV radiation with a quasar spectrum. This is used when calculating the radiation background. Default: 5e-6 Molecular Hydrogen Regulated Star Formation ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The parameters below are considered in ``StarParticleCreation`` method 11. ``H2StarMakerEfficiency`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerNumberDensityThreshold`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerMinimumMass`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerMinimumH2FractionForStarFormation`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerStochastic`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerUseSobolevColumn`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerSigmaOverR`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerAssumeColdWarmPressureBalance`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerH2DissociationFlux_MW`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerH2FloorInColdGas`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``H2StarMakerColdGasTemperature`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. ``StarFormationOncePerRootGridTimeStep`` (external) See :ref:`molecular_hydrogen_regulated_star_formation`. Population III Star Formation ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The parameters below are considered in ``StarParticleCreation`` method 3. ``PopIIIStarMass`` (external) Stellar mass of Population III stars created in ``StarParticleCreation`` method 3. Units of solar masses. The luminosities and supernova energies are calculated from Schaerer (2002) and Heger & Woosley (2002), respectively. ``PopIIIBlackHoles`` (external) Set to 1 to create black hole particles that radiate in X-rays for stars that do not go supernova (< 140 solar masses and > 260 solar masses). Default: 0. ``PopIIIBHLuminosityEfficiency`` (external) The radiative efficiency in which the black holes convert accretion to luminosity. Default: 0.1. ``PopIIIOverDensityThreshold`` (external) The overdensity threshold (relative to the total mean density) before Pop III star formation will be considered. Default: 1e6. ``PopIIIH2CriticalFraction`` (external) The H_2 fraction threshold before Pop III star formation will be considered. Default: 5e-4. ``PopIIIMetalCriticalFraction`` (external) The metallicity threshold (relative to gas density, not solar) before Pop III star formation will be considered. Note: this should be changed to be relative to solar! Default: 1e-4. ``PopIIISupernovaRadius`` (external) If the Population III star will go supernova (140