diff options
Diffstat (limited to 'fg21sim')
| -rw-r--r-- | fg21sim/configs/20-extragalactic.conf.spec | 5 | ||||
| -rw-r--r-- | fg21sim/extragalactic/clusters/halo.py | 62 |
2 files changed, 56 insertions, 11 deletions
diff --git a/fg21sim/configs/20-extragalactic.conf.spec b/fg21sim/configs/20-extragalactic.conf.spec index 042a808..3b83cb0 100644 --- a/fg21sim/configs/20-extragalactic.conf.spec +++ b/fg21sim/configs/20-extragalactic.conf.spec @@ -187,6 +187,11 @@ # Electron injection, which is assumed to have a constant injection # rate and a power-law spectrum. injection_index = float(default=2.4, min=2.1, max=3.5) + # How long the period before the merger begins, which is used to derive + # an approximately steady initial electron spectrum. During this period, + # the acceleration is turned off and only leaves energy loss mechanisms. + # Unit: [Gyr] + time_init = float(default=0.4, min=0) # Extragalactic point sources diff --git a/fg21sim/extragalactic/clusters/halo.py b/fg21sim/extragalactic/clusters/halo.py index 9c6c70e..02d8891 100644 --- a/fg21sim/extragalactic/clusters/halo.py +++ b/fg21sim/extragalactic/clusters/halo.py @@ -85,8 +85,10 @@ class RadioHalo: energy spectrum, determine the injection rate by further assuming that the total injected electrons has energy of a fraction (eta_e) of the ICM total thermal energy; - 4. Set the initial electron density/spectrum be the total injected - electrons during t_merger time; + 4. Set the electron density/spectrum be the accumulated electrons + injected during t_merger time, then evolve it for time_init period + considering only losses and constant injection, in order to derive + an approximately steady electron spectrum for following use; 5. Calculate the magnetic field from the cluster total mass (which is assumed to be growth linearly from M_main+M_sub to M_obs); 6. Calculate the energy losses for the coefficients of Fokker-Planck @@ -148,6 +150,7 @@ class RadioHalo: self.gamma_np = self.configs.getn(comp+"/gamma_np") self.buffer_np = self.configs.getn(comp+"/buffer_np") self.time_step = self.configs.getn(comp+"/time_step") + self.time_init = self.configs.getn(comp+"/time_init") self.injection_index = self.configs.getn(comp+"/injection_index") def _set_solver(self): @@ -383,6 +386,36 @@ class RadioHalo: Ke = term1 * term2 / term3 # [cm^-3 Gyr^-1] return Ke + @property + def electron_spec_init(self): + """ + The (default) initial electron spectrum at ``age_merger`` from + which to solve the final electron spectrum at the observation + time by solving the Fokker-Planck equation. + + This initial electron spectrum is derived from the accumulated + electron spectrum injected throughout the ``age_merger`` period, + by solving the same Fokker-Planck equation, but only considering + energy losses and constant injection, evolving for a period of + ``time_init`` in order to obtain an approximately steady electron + spectrum. + + Units: [cm^-3] + """ + # Accumulated electrons constantly injected until ``age_merger`` + n_inj = self.fp_injection(self.gamma) + n0_e = n_inj * self.age_merger + + logger.debug("Derive the initial electron spectrum ...") + tstart = self.age_merger - self.time_init + tstop = self.age_merger + # Use a bigger time step to save time + self.fpsolver.tstep *= 2 + n_e = self.fpsolver.solve(u0=n0_e, tstart=tstart, tstop=tstop) + # Restore the original time step + self.fpsolver.tstep = self.time_step + return n_e + def calc_electron_spectrum(self, tstart=None, tstop=None, n0_e=None): """ Calculate the relativistic electron spectrum by solving the @@ -402,8 +435,7 @@ class RadioHalo: Unit: [Gyr] n0_e : 1D `~numpy.ndarray`, optional The initial electron spectrum (number distribution). - Default: accumulated constantly injected electrons until - ``tstart``. + Default: ``self.electron_spec_init`` Unit: [cm^-3] Returns @@ -417,9 +449,7 @@ class RadioHalo: if tstop is None: tstop = self.age_obs if n0_e is None: - # Accumulated constantly injected electrons until ``tstart``. - n_inj = self.fp_injection(self.gamma) - n0_e = n_inj * tstart + n0_e = self.electron_spec_init # When the evolution time is too short, decrease the time step # to improve the results. @@ -697,11 +727,15 @@ class RadioHalo: ---------- Ref.[donnert2013],Eq.(15) """ - if t < (self.age_merger + self.time_crossing): - tau_acc = self.tau_acceleration # [Gyr] - else: - # The large enough timescale to avoid unstable results + if (t < self.age_merger) or (t > self.age_merger+self.time_crossing): + # NO acceleration; use a large enough timescale to avoid + # unstable results. tau_acc = 10.0 # [Gyr] + else: + # Turbulence acceleration + tau_acc = self.tau_acceleration # [Gyr] + + gamma = np.asarray(gamma) diffusion = gamma**2 / 4 / tau_acc return diffusion @@ -721,6 +755,12 @@ class RadioHalo: Advection coefficients, describing the energy loss/gain rates. Unit: [Gyr^-1] """ + # Always use the properties at ``age_merger`` to derive the + # initial electron spectrum. + if t < self.age_merger: + t = self.age_merger + + gamma = np.asarray(gamma) advection = (abs(self._loss_ion(gamma, t)) + abs(self._loss_rad(gamma, t)) - (self.fp_diffusion(gamma, t) * 2 / gamma)) |