From c078ca6d939e014f3c16ee239f7f97c6fc1ba7f9 Mon Sep 17 00:00:00 2001
From: Matthieu Schaller <schaller@strw.leidenuniv.nl>
Date: Wed, 13 Feb 2019 22:12:59 +0100
Subject: [PATCH] Clarify the possible temperature discrepancy between the
entropy floor and the actual gas temperature in the RTD.
---
doc/RTD/source/SubgridModels/EAGLE/index.rst | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/doc/RTD/source/SubgridModels/EAGLE/index.rst b/doc/RTD/source/SubgridModels/EAGLE/index.rst
index 0587f3f2e0..a4069bda59 100644
--- a/doc/RTD/source/SubgridModels/EAGLE/index.rst
+++ b/doc/RTD/source/SubgridModels/EAGLE/index.rst
@@ -62,12 +62,21 @@ EAGLE run, that section of the parameter file reads:
Jeans_density_threshold_H_p_cm3: 0.1 # Physical density above which the EAGLE Jeans limiter entropy floor kicks in, expressed in Hydrogen atoms per cm^3.
Jeans_over_density_threshold: 10. # Overdensity above which the EAGLE Jeans limiter entropy floor can kick in.
Jeans_temperature_norm_K: 8000 # Temperature of the EAGLE Jeans limiter entropy floor at the density threshold, expressed in Kelvin.
- Jeans_gamma_effective: 1.3333333 # Slope the of the EAGLE Jeans limiter entropy floor
+ Jeans_gamma_effective: 1.3333333 # Slope of the EAGLE Jeans limiter entropy floor
Cool_density_threshold_H_p_cm3: 1e-5 # Physical density above which the EAGLE Cool limiter entropy floor kicks in, expressed in Hydrogen atoms per cm^3.
Cool_over_density_threshold: 10. # Overdensity above which the EAGLE Cool limiter entropy floor can kick in.
Cool_temperature_norm_K: 8000 # Temperature of the EAGLE Cool limiter entropy floor at the density threshold, expressed in Kelvin.
- Cool_gamma_effective: 1. # Slope the of the EAGLE Cool limiter entropy floor
-
+ Cool_gamma_effective: 1. # Slope of the EAGLE Cool limiter entropy floor
+
+SWIFT will convert the temperature normalisations and Hydrogen number
+density thresholds into internal energies and densities respectively
+assuming a neutral gas with primoridal abundance pattern. This implies
+that the floor may not be exactly at the position given in the YAML
+file if the gas has different properties. This is especially the case
+for the temperature limit which will often be lower than the imposed
+floor by a factor :math:`\frac{\mu_{\rm neutral}}{\mu_{ionised}}
+\approx \frac{1.22}{0.59} \approx 2` due to the different ionisation
+states of the gas.
Note that the model only makes sense if the ``Cool`` threshold is at a lower
density than the ``Jeans`` threshold.
--
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