New issue 1321: Gadget Temperature field assumes zero ionization if ElectronAbundance field is not present. https://bitbucket.org/yt_analysis/yt/issues/1321/gadget-temperature-field-as... John ZuHone: In the Gadget frontend, it is assumed that if the `("PartType0", "ElectronAbundance")` field is not present, that the gas is not ionized and therefore this affects the mean molecular weight and conversely the computation of the temperature. Lines 71-89 of `yt/frontends/gadget/fields.py`: ```python def setup_gas_particle_fields(self, ptype): if (ptype, "ElectronAbundance") in self.ds.field_list: def _temperature(field, data): # Assume cosmic abundances x_H = 0.76 gamma = 5.0/3.0 a_e = data[ptype, 'ElectronAbundance'] mu = 4.0 / (3.0 * x_H + 1.0 + 4.0 * x_H * a_e) ret = data[ptype, "InternalEnergy"]*(gamma-1)*mu*mp/kb return ret.in_units(self.ds.unit_system["temperature"]) else: def _temperature(field, data): # Assume cosmic abundances x_H = 0.76 gamma = 5.0/3.0 # Assume zero ionization mu = 4.0 / (3.0 * x_H + 1.0) ret = data[ptype, "InternalEnergy"]*(gamma-1)*mu*mp/kb return ret.in_units(self.ds.unit_system["temperature"]) ``` It seems as if this is too restrictive of an assumption--there is no reason to think that simulations would not be perhaps fully ionized instead. We should find a more flexible way to define this field, perhaps by setting a field parameter for `mu`. Responsible: jzuhone