Add spin_mass_dependence option to dark_matter_halo group

The option defaults to false, and indicates whether the lognormal
distribution used to draw lambda values should use a fix value of 0.03,
or a dynamic value based on the halo spin distribution following Kim et
al. (2015), as its m parameter (the natural logarithm of the
distribution's mean).

The Lagos et al. (2023) paper used this dependency, and therefore we're
also updating the sample configuration file that reflects that paper to
ensure reproducibility.

Signed-off-by: Rodrigo Tobar <[email protected]>

include/dark_matter_halos.h

@@ -68,6 +68,7 @@ class DarkMatterHaloParameters {
 	use_converged_lambda_catalog = true, the latter will be done only for halos that have a number of particles below min_part_convergence.
 	**/
 	bool random_lambda = false;
+	bool spin_mass_dependence = false;
 	bool use_converged_lambda_catalog = false; 
 	int  min_part_convergence = 100;
 

sample.cfg

@@ -60,6 +60,7 @@ redshift_file = /path/to/simulation/redshifts.txt
 halo_profile = nfw
 lambda_random = true
 size_model = Mo98
+spin_mass_dependence = false
 
 [gas_cooling]
 lambdamodel = cloudy

sample_lagos23.cfg

@@ -55,6 +55,7 @@ halo_profile = nfw
 size_model = mo98
 lambda_random = true
 concentration_model = duffy08
+spin_mass_dependence = true
 
 [simulation]
 sim_name = mini-SURFS

src/dark_matter_halos.cpp

@@ -175,9 +175,12 @@ float DarkMatterHalos::halo_lambda (const Subhalo &subhalo, float m, double z, d
 			lambda = 1;
 	}
 
+	double lambda_cen_mhalo = 0.03;
+	if (params.spin_mass_dependence) {
+		// use a very weak dependence on Mhalo for the spin distribution, following Kim et al. (2015): arxiv:1508.06037
+		lambda_cen_mhalo = 0.00895651600584195 * std::log10(m)  - 0.07580254755439589;
+	}
 	// Prime the generator with a known seed to allow for reproducible runs
-	// using a very weak dependence on Mhalo for the spin distribution, following Kim et al. (2015): arxiv:1508.06037
-	double lambda_cen_mhalo = 0.00895651600584195 * std::log10(m)  - 0.07580254755439589;
 	std::default_random_engine generator(exec_params.get_seed(subhalo));
 	std::lognormal_distribution<double> distribution(std::log(lambda_cen_mhalo), std::abs(std::log(0.5)));
 	auto lambda_random = distribution(generator);