Motivation and description
The SpinFlipHydrogenGasMix class uses a hydrogen partitioning scheme to split neutral hydrogen (typically available from hydrodynamical cosmological simulations) into its atomic and molecular constituents. The current implementation (before this update) uses the local (based on volumetric gas density) partitioning scheme of Gnedin & Kravtsov 2011, ApJ, 728, 88. However, this scheme produces HI column densities in excess of the typically observed threshold, which is probably related to the usage of volumetric densities.
The default approach in the literature (e.g. Diemer et al., 2018, ApJS, 238, 33 and Gebek et al., 2023, MNRAS, 521, 5645) is to use column-density based partitioning schemes. To conform to this default approach which seems to yield more realistic results, this update changes the partitioning scheme implementation in SpinFlipHydrogenGasMix to the column-density based scheme of Gnedin & Draine 2014, ApJ, 795, 37.
See the SpinFlipHydrogenGasMix class header for a detailed description of the new scheme.
Incompatible changes
The new partitioning scheme causes the updated SpinFlipHydrogenGasMix class to be incompatible with the previous version. Running a ski file configuration including an "old" SpinFlipHydrogenGasMix instance will cause a fatal error. Both the ski file and the input file being imported for the gas mix must be updated manually. Because the input file changes as well, it is not possible to provide an automated update procedure.
Important changes include:
The first column of the input file after the cell/particle coordinates now describes the distribution of neutral hydrogen (as opposed to the sum of neutral and ionized hydrogen).
The last column of the input file now specifies the neutral hydrogen surface mass density, a quantity required by the new column-density-based scheme (replacing the neutral fraction in the previous scheme).
Accordingly, the defaultNeutralSurfaceDensity option replaces the previous defaultNeutralFraction option in the ski file.
Tests
The functional tests had to be updated manually for the incompatible changes listed above.
Context
This new partitioning scheme was requested and first implemented by @andreagebek.
Motivation and description The
SpinFlipHydrogenGasMixclass uses a hydrogen partitioning scheme to split neutral hydrogen (typically available from hydrodynamical cosmological simulations) into its atomic and molecular constituents. The current implementation (before this update) uses the local (based on volumetric gas density) partitioning scheme of Gnedin & Kravtsov 2011, ApJ, 728, 88. However, this scheme produces HI column densities in excess of the typically observed threshold, which is probably related to the usage of volumetric densities.The default approach in the literature (e.g. Diemer et al., 2018, ApJS, 238, 33 and Gebek et al., 2023, MNRAS, 521, 5645) is to use column-density based partitioning schemes. To conform to this default approach which seems to yield more realistic results, this update changes the partitioning scheme implementation in
SpinFlipHydrogenGasMixto the column-density based scheme of Gnedin & Draine 2014, ApJ, 795, 37.See the
SpinFlipHydrogenGasMixclass header for a detailed description of the new scheme.Incompatible changes The new partitioning scheme causes the updated
SpinFlipHydrogenGasMixclass to be incompatible with the previous version. Running a ski file configuration including an "old" SpinFlipHydrogenGasMix instance will cause a fatal error. Both the ski file and the input file being imported for the gas mix must be updated manually. Because the input file changes as well, it is not possible to provide an automated update procedure.Important changes include:
Tests The functional tests had to be updated manually for the incompatible changes listed above.
Context This new partitioning scheme was requested and first implemented by @andreagebek.