Clarify the newly added reduced Hubble constant in CGS.

src/physical_constants.c

@@ -106,11 +106,6 @@ void phys_const_init(const struct unit_system *us, struct swift_params *params,
   internal_const->const_earth_mass =
       const_earth_mass_cgs /
       units_general_cgs_conversion_factor(us, dimension_mass);
-  /* Calculate the reduced hubble constant prefactor */
-  const float dimension_hubble[5] = {0, 0, -1, 0, 0}; /* [s^-1] */
-  internal_const->const_reduced_hubble =
-      const_reduced_hubble_cgs /
-      units_general_cgs_conversion_factor(us, dimension_hubble);
 
   const float dimension_time[5] = {0, 0, 1, 0, 0}; /* [s] */
   internal_const->const_year =
@@ -136,6 +131,11 @@ void phys_const_init(const struct unit_system *us, struct swift_params *params,
   internal_const->const_primordial_He_fraction =
       const_primordial_He_fraction_cgs /
       units_general_cgs_conversion_factor(us, dimension_Yp);
+
+  const float dimension_reduced_hubble[5] = {0, 0, -1, 0, 0}; /* [s^-1] */
+  internal_const->const_reduced_hubble =
+      const_reduced_hubble_cgs /
+      units_general_cgs_conversion_factor(us, dimension_reduced_hubble);
 }
 
 /**

src/physical_constants.h

@@ -97,7 +97,7 @@ struct phys_const {
   /*! Primordial Helium fraction */
   double const_primordial_He_fraction;
 
-  /*! Unit factor of the reduced hubble constant */
+  /*! Reduced hubble constant units (i.e. H_0 / h) */
   double const_reduced_hubble;
 };
 

src/physical_constants_cgs.h

@@ -98,7 +98,8 @@ const double const_T_CMB_0_cgs = 2.7255;
 /*! Primordial Helium fraction [-] */
 const double const_primordial_He_fraction_cgs = 0.245;
 
-/*! km/s/Mpc to cgs conversion 100 * 1e5 / 3.08567781E24 */
-const double const_reduced_hubble_cgs = 3.240779e-18;
+/*! Reduced Hubble constant units (i.e. H_0 / h == 100 km / s / Mpc in CGS)
+ * [s^-1] */
+const double const_reduced_hubble_cgs = 3.2407792894458e-18;
 
 #endif /* SWIFT_PHYSICAL_CONSTANTS_CGS_H */