"""Definitions for the `BlackbodyCutoff` class."""
from math import pi
import numexpr as ne
import numpy as np
from astrocats.catalog.source import SOURCE
from astropy import constants as c
from astropy import units as u
from mosfit.constants import ANG_CGS, BOL_BAND_INDEX, FOUR_PI
from mosfit.modules.seds.sed import SED
# Important: Only define one ``Module`` class per file.
[docs]
def bbody_sup(lam, T, R2, sup_lambda, power_lambda):
'''
Calculate the corresponding blackbody radiance for a set
of wavelengths given a temperature and radiance and a
suppresion factor
Parameters
---------------
lam: Reference wavelengths in Angstroms
T: Temperature in Kelvin
R2: Radius in cm, squared
Output
---------------
Spectral radiance in units of erg/s/Angstrom
(calculation and constants checked by Sebastian Gomez)
'''
# Planck Constant in cm^2 * g / s
h = 6.62607E-27
# Speed of light in cm/s
c = 2.99792458E10
# Convert wavelength to cm
lam_cm = lam * 1E-8
# Boltzmann Constant in cm^2 * g / s^2 / K
k_B = 1.38064852E-16
# Calculate Radiance B_lam, in units of (erg / s) / cm ^ 2 / cm
exponential = (h * c) / (lam_cm * k_B * T)
B_lam = ((2 * np.pi * h * c ** 2) / (lam_cm ** 5)) / (np.exp(exponential) - 1)
# Multiply by the surface area
A = 4*np.pi*R2
# Output radiance in units of (erg / s) / Angstrom
Radiance = B_lam * A / 1E8
# Apply Supression below sup_lambda wavelength
blue = lam < sup_lambda
Radiance[blue] *= (lam[blue]/sup_lambda)**power_lambda
return Radiance
class BlackbodyCutoff(SED):
"""Blackbody SED with cutoff.
Blackbody spectral energy dist. for given temperature and radius,
with a linear absorption function bluewards of a cutoff wavelength.
"""
_REFERENCES = [
{SOURCE.BIBCODE: '2017arXiv170600825N'}
]
C_CONST = c.c.cgs.value
FLUX_CONST = FOUR_PI * (
2.0 * c.h * c.c ** 2 * pi).cgs.value * u.Angstrom.cgs.scale
X_CONST = (c.h * c.c / c.k_B).cgs.value
STEF_CONST = (4.0 * pi * c.sigma_sb).cgs.value
F_TERMS = 10
N_TERMS = 1000
def __init__(self, **kwargs):
"""Initialize module."""
super(BlackbodyCutoff, self).__init__(**kwargs)
self._nxcs = self.X_CONST * np.array(range(1, self.F_TERMS + 1))
def process(self, **kwargs):
"""Process module."""
kwargs = self.prepare_input(self.key('luminosities'), **kwargs)
self._luminosities = kwargs[self.key('luminosities')]
self._bands = kwargs['all_bands']
self._band_indices = kwargs['all_band_indices']
self._frequencies = kwargs['all_frequencies']
self._radius_phot = np.array(kwargs[self.key('radiusphot')])
self._temperature_phot = np.array(kwargs[self.key('temperaturephot')])
self._cutoff_wavelength = kwargs[self.key('cutoff_wavelength')]
self._alpha = kwargs[self.key('alpha')]
self._times = np.array(kwargs['rest_times'])
xc = self.X_CONST # noqa: F841
fc = self.FLUX_CONST
cc = self.C_CONST
ac = ANG_CGS
zp1 = 1.0 + kwargs[self.key('redshift')]
lt = len(self._times)
seds = self.alloc_seds(lt)
rp2 = self._radius_phot ** 2
tp = self._temperature_phot
evaled = False
for li, lum in enumerate(self._luminosities):
bi = self._band_indices[li]
if bi == BOL_BAND_INDEX:
continue
if lum == 0.0:
continue
if bi >= 0:
rest_wavs = self._sample_wavelengths[bi] * ac / zp1
else:
rest_wavs = np.array([cc / (self._frequencies[li] * zp1)])
# Apply absorption to SED only bluewards of cutoff wavelength
cwave_ac = self._cutoff_wavelength * ac
ab = rest_wavs < cwave_ac # noqa: F841
tpi = tp[li] # noqa: F841
rp2i = rp2[li] # noqa: F841
# Exponent of suppresion and rest wavelength should sum to 5
sup_power = self._alpha
wavs_power = (5 - sup_power)
if not evaled:
# Absorbed blackbody: 0% transmission at 0 Angstroms 100% at
# >3000 Angstroms.
sed = ne.evaluate(
"where(ab, fc * (rp2i / cwave_ac ** sup_power/ "
"rest_wavs ** wavs_power) / expm1(xc / rest_wavs / tpi), "
"fc * (rp2i / rest_wavs ** 5) / "
"expm1(xc / rest_wavs / tpi))"
)
evaled = True
else:
sed = ne.re_evaluate()
sed[np.isnan(sed)] = 0.0
if bi >= 0:
seds[li, :len(sed)] = sed
else:
seds[li, 0] = sed[0]
uniq_times = np.unique(self._times)
tsort = np.argsort(self._times)
uniq_is = np.searchsorted(self._times, uniq_times, sorter=tsort)
bb_wavelengths = np.linspace(100, 100000, self.N_TERMS)
norms = np.array([(R2 * self.STEF_CONST * T ** 4) / np.trapezoid(bbody_sup(bb_wavelengths,T,R2,self._cutoff_wavelength,self._alpha), bb_wavelengths) for T, R2 in zip(tp[uniq_is],rp2[uniq_is])])
# Apply renormalisation
seds *= norms[np.searchsorted(uniq_times, self._times)][:, None]
seds = self.add_to_existing_seds(seds, **kwargs)
# Units of `seds` is ergs / s / Angstrom.
return {'sample_wavelengths': self._sample_wavelengths,
self.key('seds'): seds,
'luminosities_out': self._luminosities,
'times_out': self._times
}