Read the maximal BH mass to reposition from the parameter file.

examples/EAGLE_low_z/EAGLE_6/eagle_6.yml

@@ -171,3 +171,4 @@ EAGLEAGN:
   coupling_efficiency:              0.15       # 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.
   AGN_num_ngb_to_heat:              1.         # Target number of gas neighbours to heat in an AGN feedback event.
+  max_reposition_mass:              2e8        # Maximal BH mass considered for BH repositioning in solar masses.
\ No newline at end of file

src/black_holes/EAGLE/black_holes.h

@@ -24,6 +24,7 @@
 #include "black_holes_struct.h"
 #include "cosmology.h"
 #include "dimension.h"
+#include "gravity.h"
 #include "kernel_hydro.h"
 #include "minmax.h"
 #include "physical_constants.h"
@@ -457,6 +458,24 @@ __attribute__((always_inline)) INLINE static void black_holes_prepare_feedback(
   }
 }
 
+__attribute__((always_inline)) INLINE static void
+black_holes_end_reposition(struct bpart* restrict bp,
+			   const struct black_holes_props* props,
+			   const struct phys_const* constants,
+			   const struct cosmology* cosmo) {
+
+  const float potential = gravity_get_comoving_potential(bp->gpart);
+
+  /* Is the potential lower (i.e. the BH is at the bottom already)
+   * OR is the BH massive enough that we don't reposition? */
+  if (potential < bp->reposition.min_potential ||
+      bp->subgrid_mass > props->max_reposition_mass) {
+
+    /* No need to reposition */
+    bp->reposition.min_potential = FLT_MAX;
+  }
+}
+
 /**
  * @brief Reset acceleration fields of a particle
  *

src/black_holes/EAGLE/black_holes_properties.h

@@ -74,6 +74,11 @@ struct black_holes_props {
   /*! Number of gas neighbours to heat in a feedback event */
   float num_ngbs_to_heat;
 
+  /* ---- Properties of the repositioning model --- */
+
+  /*! Maximal mass of BH to reposition */
+  float max_reposition_mass;
+
   /* ---- Common conversion factors --------------- */
 
   /*! Conversion factor from temperature to internal energy */
@@ -157,6 +162,14 @@ INLINE static void black_holes_props_init(struct black_holes_props *bp,
   bp->num_ngbs_to_heat =
       parser_get_param_float(params, "EAGLEAGN:AGN_num_ngb_to_heat");
 
+  /* Reposition parameters --------------------------------- */
+
+  bp->max_reposition_mass =
+      parser_get_param_float(params, "EAGLEAGN:max_reposition_mass");
+
+  /* Convert to internal units */
+  bp->max_reposition_mass *= phys_const->const_solar_mass;
+
   /* Common conversion factors ----------------------------- */
 
   /* Calculate temperature to internal energy conversion factor (all internal

src/runner.c

@@ -905,6 +905,10 @@ void runner_do_black_holes_swallow_ghost(struct runner *r, struct cell *c,
 
       if (bpart_is_active(bp, e)) {
 
+        /* Compute the final operations for repositioning of this BH */
+        black_holes_end_reposition(bp, e->black_holes_properties,
+				   e->physical_constants, e->cosmology);
+
         /* Get particle time-step */
         double dt;
         if (with_cosmology) {