From 21f5b0c8e0957b7af311bcaa6f10cfbce9f60ade Mon Sep 17 00:00:00 2001
From: Matthieu Schaller <schaller@strw.leidenuniv.nl>
Date: Sat, 12 Jan 2019 21:23:46 +0100
Subject: [PATCH] Small clarification about the Helium fraction in the EAGLE
cooling code.
---
src/cooling/EAGLE/cooling.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/src/cooling/EAGLE/cooling.c b/src/cooling/EAGLE/cooling.c
index a08a427440..3ca3eb5218 100644
--- a/src/cooling/EAGLE/cooling.c
+++ b/src/cooling/EAGLE/cooling.c
@@ -499,14 +499,13 @@ void cooling_cool_part(const struct phys_const *restrict phys_const,
float abundance_ratio[chemistry_element_count + 2];
abundance_ratio_to_solar(p, cooling, abundance_ratio);
- /* Get the Hydrogen mass fraction */
+ /* Get the Hydrogen and Helium mass fractions */
const float XH = p->chemistry_data.metal_mass_fraction[chemistry_element_H];
+ const float XHe = p->chemistry_data.metal_mass_fraction[chemistry_element_He];
/* Get the Helium mass fraction. Note that this is He / (H + He), i.e. a
* metal-free Helium mass fraction as per the Wiersma+08 definition */
- const float HeFrac =
- p->chemistry_data.metal_mass_fraction[chemistry_element_He] /
- (XH + p->chemistry_data.metal_mass_fraction[chemistry_element_He]);
+ const float HeFrac = XHe / (XH + XHe);
/* convert Hydrogen mass fraction into Hydrogen number density */
const double n_H =
@@ -707,14 +706,13 @@ float cooling_get_temperature(
const float u = hydro_get_physical_internal_energy(p, xp, cosmo);
const double u_cgs = u * cooling->internal_energy_to_cgs;
- /* Get the Hydrogen mass fraction */
+ /* Get the Hydrogen and Helium mass fractions */
const float XH = p->chemistry_data.metal_mass_fraction[chemistry_element_H];
+ const float XHe = p->chemistry_data.metal_mass_fraction[chemistry_element_He];
/* Get the Helium mass fraction. Note that this is He / (H + He), i.e. a
* metal-free Helium mass fraction as per the Wiersma+08 definition */
- const float HeFrac =
- p->chemistry_data.metal_mass_fraction[chemistry_element_He] /
- (XH + p->chemistry_data.metal_mass_fraction[chemistry_element_He]);
+ const float HeFrac = XHe / (XH + XHe);
/* Convert Hydrogen mass fraction into Hydrogen number density */
const float rho = hydro_get_physical_density(p, cosmo);
--
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