Parameters and Data Files

Parameters

For all on/off integer flags, 0 is off and 1 is on.

use_grackle (int)
Flag to activate the grackle machinery. Default: 0.
with_radiative_cooling (int)
Flag to include radiative cooling and actually update the thermal energy during the chemistry solver. If off, the chemistry species will still be updated. The most common reason to set this to off is to iterate the chemistry network to an equilibrium state. Default: 1.
primordial_chemistry (int)

Flag to control which primordial chemistry network is used. Default: 0.

  • 0: no chemistry network. Radiative cooling for primordial species is solved by interpolating from lookup tables calculated with Cloudy. A simplified set of functions are available (though not required) for use in this mode. For more information, see Pure Tabulated Mode.
  • 1: 6-species atomic H and He. Active species: H, H+, He, He+, ++, e-.
  • 2: 9-species network including atomic species above and species for molecular hydrogen formation. This network includes formation from the H- and H2+ channels, three-body formation (H+H+H and H+H+H2), H2 rotational transitions, chemical heating, and collision-induced emission (optional). Active species: above + H-, H2, H2+.
  • 3: 12-species network include all above plus HD rotation cooling. Active species: above plus D, D+, HD.

Note

In order to make use of the non-equilibrium chemistry network (primordial_chemistry options 1-3), you must add and advect baryon fields for each of the species used by that particular option.

h2_on_dust (int)
  • Flag to enable H2 formation on dust grains, dust cooling, and dust-gas heat transfer follow Omukai (2000). This assumes that the dust to gas ratio scales with the metallicity. Default: 0.
metal_cooling (int)
Flag to enable metal cooling using the Cloudy tables. If enabled, the cooling table to be used must be specified with the grackle_data_file parameter. Default: 0.

Note

In order to use the metal cooling, you must add and advect a metal density field.

cmb_temperature_floor (int)
Flag to enable an effective CMB temperature floor. This is implemented by subtracting the value of the cooling rate at TCMB from the total cooling rate. Default: 1.
UVbackground (int)
Flag to enable a UV background. If enabled, the cooling table to be used must be specified with the grackle_data_file parameter. Default: 0.
grackle_data_file (string)
Path to the data file containing the metal cooling and UV background tables. Default: “”.
Gamma (float)
The ratio of specific heats for an ideal gas. A direct calculation for the molecular component is used if primordial_chemistry > 1. Default: 5/3.
three_body_rate (int)
Flag to control which three-body H2 formation rate is used. 0: Abel, Bryan & Norman (2002), 1: Palla, Salpeter & Stahler (1983), 2: Cohen & Westberg (1983), 3: Flower & Harris (2007), 4: Glover (2008). These are discussed in Turk et. al. (2011). Default: 0.
cie_cooling (int)
Flag to enable H2 collision-induced emission cooling from Ripamonti & Abel (2004). Default: 0.
h2_optical_depth_approximation (int)
Flag to enable H2 cooling attenuation from Ripamonti & Abel (2004). Default: 0.
photoelectric_heating (int)
Flag to enable a spatially uniform heating term approximating photo-electric heating from dust from Tasker & Bryan (2008). Default: 0.
photoelectric_heating_rate (float)
If photoelectric_heating enabled, the heating rate in units of erg cm-3 s-1. Default: 8.5e-26.
Compton_xray_heating (int)
Flag to enable Compton heating from an X-ray background following Madau & Efstathiou (1999). Default: 0.
LWbackground_intensity (float)
Intensity of a constant Lyman-Werner H2 photo-dissociating radiation field in units of 10-21 erg s-1 cm-2 Hz-1 sr-1. Default: 0.
LWbackground_sawtooth_suppression (int)
Flag to enable suppression of Lyman-Werner flux due to Lyman-series absorption (giving a sawtooth pattern), taken from Haiman & Abel, & Rees (2000). Default: 0.

Data Files

These files contain the metal heating and cooling rates and the UV background photo-heating and photo-ionization rates. For all three files, the number density range is -10 < log10 (nH / cm-3) < 4 and the temperature range is 1 < log10 (T / K) < 9. Extrapolation is performed when outside of the data range. All data files are located in the input directory in the source.

  • CloudyData_noUVB.h5 - metal cooling rates for collisional ionization equilibrium.
  • CloudyData_UVB=FG2011.h5 - metal heating and cooling rates and UV background rates from the work of Faucher-Giguere et. al. (2009), updated in 2011. The maxmimum redshift is 10.6. Above that, collisional ionization equilibrium is assumed.
  • CloudyData_UVB=HM2012.h5 - metal heating and cooling rates and UV background rates from the work of Haardt & Madau (2012). The maximum redshift is 15.13. Above that, collisional ionization equilibrium is assumed.