Adaptive AGN heating temperature jump

This merge request implements a model to adaptively calculate the AGN heating temperature jump dT, rather than using a prescribed constant value.

dT is calculated as min(max(dT_min, dT_mass, dT_crit, dT_local), dT_max), where:

• dT_min and dT_max are (constant) min/max values for dT (default: 1e7 K, 3e9 K)
• dT_mass = theta * (m_BH / m_ref)^beta (with theta, m_ref, and beta as free parameters, and m_BH the subgrid mass of the BH). This is intended as a proxy for a scaling with virial halo temperature, assuming that m_BH is proportional to M_halo. Beta is then fixed at 2/3. The default values for theta and m_ref are 3e8 K and 1e8 M_sun, respectively; tests in 25 Mpc boxes show little impact of the exact values.
• dT_crit is the critical temperature required to avoid numerical cooling losses according to Dalla Vecchia & Schaye (2012), multiplied by an arbitrary factor (default: 1).
• dT_local is the (SPH-smoothed) average gas temperature in the kernel, multiplied with an arbitrary factor (default: 0, i.e. do not take local temperature into account).

So far, only the EAGLE_ICs/EAGLE_25 parameter example is updated with the new parameters.

examples/EAGLE_ICs/EAGLE_100/eagle_100.yml

@@ -217,7 +217,16 @@ EAGLEAGN:
   max_eddington_fraction:             1.         # Maximal allowed accretion rate in units of the Eddington rate.
   eddington_fraction_for_recording:   0.1        # Record the last time BHs reached an Eddington ratio above this threshold.
   coupling_efficiency:                0.1        # Fraction of the radiated energy that couples to the gas in feedback events.
-  AGN_delta_T_K:                      3.16228e8  # Change in temperature to apply to the gas particle in an AGN feedback event in Kelvin.
+  use_variable_delta_T:               1          # Switch to enable adaptive calculation of AGN dT [1], rather than using a constant value [0].
+  AGN_with_locally_adaptive_delta_T:  1          # Switch to enable additional dependence of AGN dT on local gas density and temperature (only used if use_variable_delta_T is 1).
+  AGN_delta_T_mass_norm:              3e8        # Normalisation temperature of AGN dT scaling with BH subgrid mass [K] (only used if use_variable_delta_T is 1).
+  AGN_delta_T_mass_reference:         1e8        # BH subgrid mass at which the normalisation temperature set above applies [M_Sun] (only used if use_variable_delta_T is 1).
+  AGN_delta_T_mass_exponent:          0.666667.  # Power-law index of AGN dT scaling with BH subgrid mass (only used if use_variable_delta_T is 1).
+  AGN_delta_T_crit_factor:            1.0        # Multiple of critical dT for numerical efficiency (Dalla Vecchia & Schaye 2012) to use as dT floor (only used if use_variable_delta_T and AGN_with_locally_adaptive_delta_T are both 1).
+  AGN_delta_T_background_factor:      0.0        # Multiple of local gas temperature to use as dT floor (only used if use_variable_delta_T and AGN_with_locally_adaptive_delta_T are both 1).
+  AGN_delta_T_min:                    1e7        # Minimum allowed value of AGN dT [K] (only used if use_variable_delta_T is 1).
+  AGN_delta_T_max:                    3e9        # Maximum allowed value of AGN dT [K] (only used if use_variable_delta_T is 1).
+  AGN_delta_T_K:                      3.16228e8  # Change in temperature to apply to the gas particle in an AGN feedback event [K] (only used if use_variable_delta_T is 0).
   AGN_num_ngb_to_heat:                1.         # Target number of gas neighbours to heat in an AGN feedback event.
   max_reposition_mass:                1e20       # Maximal BH mass considered for BH repositioning in solar masses (large number implies we always reposition).
   max_reposition_distance_ratio:      3.0        # Maximal distance a BH can be repositioned, in units of the softening length.