Skip to content

Tutorial: Dark matter subhalo evolution

Jump to bottom
Andrew Benson edited this page Feb 9, 2021 · 7 revisions

In this tutorial we'll use Galacticus to evolve populations of subhalos within a dark matter halo merger tree and output their properties. No baryonic physics (well, almost no baryonic physics) is included in this model.

If you haven't already installed Galacticus, you can find the installation instructions here.

Running the calculation

For this tutorial we'll use the parameters/tutorials/darkMatterOnlySubHalos.xml parameter file:

$ ./Galacticus.exe parameters/tutorials/darkMatterOnlySubHalos.xml

If everything is working you should see output which looks something like:

              ##                                     
   ####        #                  #                  
  #   #        #             #                       
 #       ###   #  ###   ### ###  ##   ### ## ##   ## 
 #       #  #  #  #  # #  #  #    #  #  #  #  #  #   
 #   ###  ###  #   ### #     #    #  #     #  #   #  
  #   #  #  #  #  #  # #     #    #  #     #  #    # 
   ####  #### ### ####  ###   ## ###  ###   #### ##  

 © 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
   2017, 2018, 2019, 2020, 2021
   - Andrew Benson

M: Memory:         code +      nodes +       misc =      total
M:            22.246Mib +   1.000  b +   9.000  b =  22.246Mib
M: -> Begin multiple tasks
.
.
.

and a file darkMatterOnlySubHalos.hdf5 will have been created. Typically this model will take around XXXX to run, but it may be slower the first time you run it as various power spectra are computed and stored.

Understanding the input

You can look at the entire parameter file for this tutorial here. Below we'll explore sections of the file to understand what they do. (Sections that have been explored in previous tutorials, e.g. cosmological parameters, will not be reexamined here.)

  <!-- Task -->
  <taskMethod                   value="multi"  >
    <taskMethod value="powerSpectra"      >
      <wavenumberMinimum value="1.0e-3"/>
      <wavenumberMaximum value="1.0e+2"/>
      <pointsPerDecade   value="10"    />
    </taskMethod>
    <taskMethod value="haloMassFunction"  >
      <haloMassMinimum value="1.0e06"/>
      <haloMassMaximum value="1.0e15"/>
      <pointsPerDecade value="10"    />
    </taskMethod>
    <taskMethod value="evolveForests"    />
  </taskMethod>
  <evolveForestsWorkShareMethod value="cyclic"/>

This block tells Galacticus what task we want it to perform - here we're just asking it to compute the power spectrum, the halo mass function, and then to evolve merger tree forests.

  <!-- Structure formation options -->
  <linearGrowthMethod          value="baryonsDarkMatter"                    />
  <criticalOverdensityMethod   value="sphericalCollapseBrynsDrkMttrDrkEnrgy"/>
  <virialDensityContrastMethod value="sphericalCollapseBrynsDrkMttrDrkEnrgy"/>
  <haloMassFunctionMethod      value="shethTormen"                           >
    <a             value="0.791"/> <!-- Best fit values from Benson, Ludlow, & Cole (2019). -->
    <normalization value="0.302"/>
    <p             value="0.218"/>
  </haloMassFunctionMethod>
  <excursionSetBarrierMethod value="remapScale"     >
    <!-- Remap the barrier height by a constant factor to account for the difference in sigma(M) on large scales introduced by our
         choice of using a sharp-in-k-space filter on the power spectrum. -->
    <factor                    value="1.1965"            />
    <applyTo                   value="nonRates"          />
    <!-- Remap the barrier height according to the parameterization of Sheth, Mo, & Tormen (2001) to account for ellipsoidal
         collapse. -->
    <excursionSetBarrierMethod value="remapShethMoTormen" >
      <a                         value="0.707"              />
      <b                         value="0.500"              />
      <c                         value="0.600"              />
      <applyTo                   value="nonRates"           />
      <!-- Use the critical overdensity as the barrier height in the excursion set problem. -->
      <excursionSetBarrierMethod value="criticalOverdensity"/>
    </excursionSetBarrierMethod>
  </excursionSetBarrierMethod>
  <excursionSetFirstCrossingMethod value="linearBarrier"/>

This block specifies various options related to large scale structure growth. The linear growth function is set to the baryonsDarkMatter model of Benson (2020), in which the suppression of growth of large wavenumber modes due to baryon pressure is accounted for. Options for solving the excursion set problem are also included here, even though it is not used with the Sheth & Tormen (2002) mass function which we select. It is included since it is required if the mass function is switched to the [Press & Schechter (1974)[http://adsabs.harvard.edu/abs/1974ApJ...187..425P] form used for some non-CDM dark matter models.

  <intergalacticMediumStateMethod value="instantReionization">
    <reionizationRedshift           value="8.0e0"  />
    <reionizationTemperature        value="1.5e4"  />
    <presentDayTemperature          value="1.0e3"  />
    <intergalacticMediumStateMethod value="recFast"/>
  </intergalacticMediumStateMethod>

Here we select a simple model of the evolution of the IGM. The thermal history of the IGM is needed to solve for the growth of large wavenumber modes where baryon pressure delays the growth of structure. This IGM model assumes instant reionization at z=8, heating to a temperature of 15,000K, and cooling to 1,000K by the present day. Prior to reionization the IGM state is computed using the RecFast code.

  <!-- Dark matter halo structure options -->
  <darkMatterProfileDMOMethod         value="heated"              >
    <darkMatterProfileDMOMethod value="NFW"      />
    <nonAnalyticSolver          value="numerical"/>
  </darkMatterProfileDMOMethod>
  <darkMatterProfileHeatingMethod     value="tidal"              />
  <darkMatterProfileScaleRadiusMethod value="ludlow2016"          >
    <C                                  value="700.27000"    /> <!-- Best fit values from Johnson, Benson, & Grin (2020). -->
    <f                                  value="  0.07534"    />
    <timeFormationSeekDelta             value="  0.00000"    />
    <darkMatterProfileScaleRadiusMethod value="concentration" >
      <correctForConcentrationDefinition    value="true"              />
      <darkMatterProfileConcentrationMethod value="diemerKravtsov2014" >
	<alpha   value="1.12"/>
	<beta    value="1.69"/>
	<eta0    value="6.82"/>
	<eta1    value="1.42"/>
	<kappa   value="0.69"/>
	<phi0    value="6.58"/>
	<phi1    value="1.37"/>
	<scatter value="0.00"/>
      </darkMatterProfileConcentrationMethod>
    </darkMatterProfileScaleRadiusMethod>
  </darkMatterProfileScaleRadiusMethod>
  <darkMatterProfileMinimumConcentration value="  4.0"/>
  <darkMatterProfileMaximumConcentration value="100.0"/>

  <!-- Concentration model -->
  <darkMatterProfileScaleVirialTheoremUnresolvedEnergy value="0.5500"/> <!-- Best fit value from Johnson, Benson, & Grin (2020) -->
  <darkMatterProfileScaleVirialTheoremMassExponent     value="1.5552"/>
  <darkMatterProfileScaleVirialTheoremEnergyBoost      value="0.6773"/>

Here we select our model for dark matter halo profiles - we use an NFW profile but allowing for "heating" of the profile as described in Pullen et al. (2016). We also define parameters of the concentration model. In this model scale radii of halos are computed using the random walk approach of Johnson, Benson & Grin (2021). The parameters of that model are given here, along with the parameters of the "fallback" model used for nodes in the merger tree for which the random walk model can not be applied.

  <!-- Dark matter halo spin -->
  <haloSpinDistributionMethod value="bett2007"> <!-- Values from Benson (2017) -->
    <alpha   value="1.7091800"/>
    <lambda0 value="0.0420190"/>
  </haloSpinDistributionMethod>
  <spinVitvitskaMassExponent value="0.10475"/> <!-- Best fit value from Benson, Behrens, & Lu (2020) -->

Halo spin parameters are also modeled using a random walk approach Benson, Behrens & Lu (2020) - here we specify the parameters of that random walk model and a "fallback" spin distribution to be used for halos for which the random walk model can not be applied.

  <!-- Halo accretion options -->
  <accretionHaloMethod value="zero"/>

  <!-- Hot halo gas model options -->
  <hotHaloMassDistributionMethod value="null"          />

  <!-- Galactic structure solver options -->
  <galacticStructureSolverMethod value="null"          />
  <darkMatterProfileMethod       value="darkMatterOnly"/>

  <!-- Galaxy mergers -->
  <mergerRemnantSizeMethod value="null"/>

The preceeding block acts to switch off various baryonic physics which we want to exclude from this model.

  <!-- Satellite orbit options -->
  <virialOrbitMethod value="spinCorrelated">
    <alpha             value="0.47263"  /> <!-- Best fit value from Benson, Behrens, & Lu (2020) -->
    <virialOrbitMethod value="jiang2014" >
      <!-- Best fit value from Benson, Behrens, & Lu (2020) -->
      <bRatioHigh             value="+2.88333 +4.06371 +3.86726"/>
      <bRatioIntermediate     value="+1.05361 +1.56868 +2.89027"/>
      <bRatioLow              value="+0.07432 +0.54554 +1.04721"/>
      <gammaRatioHigh         value="+0.07124 +0.04737 -0.01913"/>
      <gammaRatioIntermediate value="+0.10069 +0.07821 +0.04231"/>
      <gammaRatioLow          value="+0.10866 +0.11260 +0.11698"/>
      <muRatioHigh            value="+1.10168 +1.09639 +1.09819"/>
      <muRatioIntermediate    value="+1.18205 +1.19573 +1.24581"/>
      <muRatioLow             value="+1.22053 +1.22992 +1.25528"/>
      <sigmaRatioHigh         value="+0.09244 +0.14335 +0.21079"/>
      <sigmaRatioIntermediate value="+0.07397 +0.09590 +0.10941"/>
      <sigmaRatioLow          value="+0.07458 +0.09040 +0.06981"/>
    </virialOrbitMethod>
  </virialOrbitMethod>
  <satelliteOrbitStoreOrbitalParameters value="true"/>

When halos first become subhalos they are assigned orbital parameters. The above defines the distribution of those parameters, using the Jiang et al. (2015) model for the distribution of radial and tangential velocities, plus the model of Benson, Behrens & Lu (2020) for the anisotropy of the distribution of orbits.

  <!-- Orbiting model of satellites -->
  <!-- Values taken from Yang et al. (2020) for their gamma=0 case using the Caterpillar simulations as calibration target -->
  <satelliteDynamicalFrictionMethod value="chandrasekhar1943">
    <logarithmCoulomb value="1.53"/>
  </satelliteDynamicalFrictionMethod>
  <satelliteTidalHeatingRateMethod  value="gnedin1999"       >
    <epsilon          value="0.33"/>
    <gamma            value="0.00"/>
  </satelliteTidalHeatingRateMethod>
  <satelliteTidalStrippingMethod    value="zentner2005"      >
    <efficiency       value="2.86"/>
  </satelliteTidalStrippingMethod>

Here we define parameters of the various physics models applied to the evolution of subhalos, as outlined in Yang et al. (2020).

  <!-- Node evolution and physics -->
  <nodeOperatorMethod value="multi">
    <!-- Subhalo hierarchy -->
    <nodeOperatorMethod value="subsubhaloPromotion"   />
    <!-- Subhalo orbits -->
    <nodeOperatorMethod value="satelliteOrbit"                   />
    <nodeOperatorMethod value="satelliteDynamicalFriction"       />
    <nodeOperatorMethod value="satelliteTidalMassLoss"           />
    <nodeOperatorMethod value="satelliteTidalHeating"            />
    <nodeOperatorMethod value="satelliteMergingRadiusTrigger"     >
      <radiusVirialFraction      value="0.01"/>
    </nodeOperatorMethod>
    <nodeOperatorMethod value="satelliteDestructionMassThreshold" >
      <massDestruction           value="=[mergerTreeMassResolutionMethod::massResolution]"/>
      <massDestructionFractional value="0.0e0"/>
    </nodeOperatorMethod>
  </nodeOperatorMethod>

This block applies various physical processes to subhalos.


  <!-- Output options -->
  <galacticusOutputFileName value="darkMatterOnlySubHalos.hdf5"/>
  <mergerTreeOutputterMethod value="multi">
    <mergerTreeOutputterMethod value="standard">
      <outputReferences value="false"/>
    </mergerTreeOutputterMethod>
    <mergerTreeOutputterMethod value="analyzer"/>
  </mergerTreeOutputterMethod>
  <outputTimesMethod value="list">
    <redshifts value="0.5"/>
  </outputTimesMethod>
  <nodePropertyExtractorMethod value="multi">
    <nodePropertyExtractorMethod value="nodeIndices"          />
    <nodePropertyExtractorMethod value="indicesTree"          />
    <nodePropertyExtractorMethod value="redshiftLastIsolated" />
    <nodePropertyExtractorMethod value="radiusTidal"          />
    <nodePropertyExtractorMethod value="radiusBoundMass"      />
    <nodePropertyExtractorMethod value="virialProperties"     />
    <nodePropertyExtractorMethod value="radiusVelocityMaximum"/>
    <nodePropertyExtractorMethod value="velocityMaximum"      />
    <nodePropertyExtractorMethod value="positionOrbital"      />
    <nodePropertyExtractorMethod value="densityProfile"        >
      <includeRadii     value="true"                                                                                                                                                                            />
      <radiusSpecifiers value="darkMatterScaleRadius:all:all:0.3 darkMatterScaleRadius:all:all:1.0 darkMatterScaleRadius:all:all:3.0 virialRadius:all:all:0.1 virialRadius:all:all:0.3 virialRadius:all:all:1.0"/>
    </nodePropertyExtractorMethod>
    <nodePropertyExtractorMethod value="projectedDensity"     >
      <includeRadii     value="true"                                                                                                                                                                            />
      <radiusSpecifiers value="darkMatterScaleRadius:all:all:0.3 darkMatterScaleRadius:all:all:1.0 darkMatterScaleRadius:all:all:3.0 virialRadius:all:all:0.1 virialRadius:all:all:0.3 virialRadius:all:all:1.0"/>
    </nodePropertyExtractorMethod>
  </nodePropertyExtractorMethod>
  <outputAnalysisMethod value="multi">
    <outputAnalysisMethod value="subhaloMassFunction">
      <fileName                          value="%DATASTATICPATH%/darkMatter/subhaloDistributionsCaterpillar.hdf5"/>
      <negativeBinomialScatterFractional value="0.18"                                                            /> <!-- Boylan-Kolchin et al. (2010) -->
      <virialDensityContrastMethod       value="bryanNorman1998"                                                 />
      <redshift                          value="0.0"                                                             />
    </outputAnalysisMethod>
    <outputAnalysisMethod value="subhaloRadialDistribution">
      <fileName                          value="%DATASTATICPATH%/darkMatter/subhaloDistributionsCaterpillar.hdf5"/>
      <negativeBinomialScatterFractional value="0.18"                                                            /> <!-- Boylan-Kolchin et al. (2010) -->
      <virialDensityContrastMethod       value="bryanNorman1998"                                                 />
      <redshift                          value="0.0"                                                             />
    </outputAnalysisMethod>
    <outputAnalysisMethod value="subhaloVMaxVsMass">
      <fileName                          value="%DATASTATICPATH%/darkMatter/subhaloDistributionsCaterpillar.hdf5"/>
      <virialDensityContrastMethod       value="bryanNorman1998"                                                 />
      <redshift                          value="0.0"                                                             />
    </outputAnalysisMethod>
  </outputAnalysisMethod>

Finally we specify the outputs that we want. Here we request a number of additional properties to be output, and also request thee summary analyses (subhalo mass function, Vmax function, and radial distribution - each compared to results from the Caterpillar simulations) to be computed and output.

Understanding the output

The main output follows the general form described in the tutorial on dark matter only merger trees, but with some additional properties (subhalo orbital positions, tidal radii, etc.)

In addition, there is now an analyses group:

Clone this wiki locally