clusters/main.py: Implement "_simulate_merger()"

Simulate the formation history of each cluster and identify the
last/recent major merger event.

Also add new configuration option "tau_merger" and tweak several
configurations options.

Signed-off-by: Aaron LI <aly@aaronly.me>

1 files changed, 19 insertions, 9 deletions

diff --git a/fg21sim/configs/20-extragalactic.conf.spec b/fg21sim/configs/20-extragalactic.conf.spec
index 377bd27..0f797a8 100644
--- a/fg21sim/configs/20-extragalactic.conf.spec
+++ b/fg21sim/configs/20-extragalactic.conf.spec
@@ -16,13 +16,31 @@
 
 [extragalactic]
 
-  # Emissions from the clusters of galaxies
+  # Extended emissions from the clusters of galaxies
+  # The configurations in this ``[[clusters]]`` section may also be
+  # used by the following ``[[halos]]`` section.
   [[clusters]]
   # The clusters catalog derived from the Hubble Volume Project (CSV file)
   catalog = string(default=None)
   # Output the effective/inuse clusters catalog data (CSV file)
   catalog_outfile = string(default=None)
 
+  # Minimum mass change of the main cluster to be regarded as a merger
+  # event instead of an accretion event.
+  # Unit: [Msun]
+  merger_mass_min = float(default=1e12, min=1e10, max=1e14)
+
+  # Mass ratio of the main and sub clusters, below which is regarded as
+  # a major merger event.
+  ratio_major = float(default=3.0, min=1.0, max=10.0)
+
+  # The merger timescale, which roughly describes the duration of the
+  # merger-induced disturbance (~2-3 Gyr).  This timescale is much longer
+  # the merger crossing time (~1 Gyr), and is also longer than the lifetime
+  # of radio halos.
+  # Unit: [Gyr]
+  tau_merger = float(default=3.0, min=1.0, max=5.0)
+
   # The fraction that a cluster hosts a radio halo
   halo_fraction = float(default=None, min=0.0, max=1.0)
 
@@ -51,14 +69,6 @@
   # merger. (unit: Msun)
   merger_mass_th = float(default=1e13, min=1e12)
 
-  # Minimum mass change of the main-cluster to be regarded as a merger
-  # event rather than accretion. (unit: Msun)
-  merger_mass_min = float(default=1e12, min=1e10)
-
-  # Mass ratio of the main and sub clusters, below which is regarded as
-  # a major merger event.
-  ratio_major = float(default=3.0, min=1.0, max=10.0)
-
   # Radius of the giant radio halo in clusters (unit: kpc)
   # XXX: currently only support a constant radius of halos
   radius = float(default=500.0, min=100.0)