Add the light-weight nebular module that absorbs the nebular continuum but does not emit anything.

pcigale/creation_modules/nebular_noemission.py

+# -*- coding: utf-8 -*-
+# Copyright (C) 2014 University of Cambridge
+# Licensed under the CeCILL-v2 licence - see Licence_CeCILL_V2-en.txt
+# Author: Médéric Boquien <mboquien@ast.cam.ac.uk>
+
+from collections import OrderedDict
+
+import numpy as np
+import scipy.constants as cst
+
+from pcigale.data import Database
+from . import CreationModule
+
+
+class NebularEmission(CreationModule):
+    """
+    Module computing the nebular emission from the ultraviolet to the
+    near-infrared. It includes both the nebular lines and the nubular
+    continuum. It takes into account the escape fraction and the absorption by
+    dust.
+
+    Given the number of Lyman continuum photons, we compute the Hβ line
+    luminosity. We then compute the other lines using the
+    metallicity-dependent templates that provide the ratio between individual
+    lines and Hβ. The nebular continuum is scaled directly from the number of
+    ionizing photons.
+
+    """
+
+    parameter_list = OrderedDict([
+        ('f_esc', (
+            'float',
+            "Fraction of Lyman continuum photons escaping the galaxy",
+            0.
+        )),
+        ('f_dust', (
+            'float',
+            "Fraction of Lyman continuum photons absorbed by dust",
+            0.
+        ))
+    ])
+
+    def _init_code(self):
+        """Get the nebular emission lines out of the database and resample
+           them to see the line profile. Compute scaling coefficients.
+        """
+
+        fesc = self.parameters['f_esc']
+        fdust = self.parameters['f_dust']
+
+        if fesc < 0. or fesc > 1:
+            raise Exception("Escape fraction must be between 0 and 1")
+
+        if fdust < 0 or fdust > 1:
+            raise Exception("Fraction of lyman photons absorbed by dust must "
+                            "be between 0 and 1")
+
+        if fesc + fdust > 1:
+            raise Exception("Escape fraction+f_dust>1")
+
+        self.idx_Ly_break = None
+        self.absorbed_old = None
+        self.absorbed_young = None
+
+    def process(self, sed):
+        """Add the nebular emission lines
+
+        Parameters
+        ----------
+        sed: pcigale.sed.SED object
+        parameters: dictionary containing the parameters
+
+        """
+        if self.idx_Ly_break is None:
+            self.idx_Ly_break = np.searchsorted(sed.wavelength_grid, 91.)
+            self.absorbed_old = np.zeros(sed.wavelength_grid.size)
+            self.absorbed_young = np.zeros(sed.wavelength_grid.size)
+        self.absorbed_old[:self.idx_Ly_break] -= sed.get_lumin_contribution('stellar.old')[:self.idx_Ly_break] * (1. - self.parameters['f_esc'])
+        self.absorbed_young[:self.idx_Ly_break] -= sed.get_lumin_contribution('stellar.young')[:self.idx_Ly_break] * (1. - self.parameters['f_esc'])
+
+        sed.add_module(self.name, self.parameters)
+        sed.add_info('nebular.f_esc', self.parameters['f_esc'])
+        sed.add_info('nebular.f_dust', self.parameters['f_dust'])
+        sed.add_info('dust.luminosity', (sed.info['stellar.lum_ly_young'] +
+                     sed.info['stellar.lum_ly_old']) *
+                     self.parameters['f_dust'], True)
+
+        sed.add_contribution('nebular.absorption_old', sed.wavelength_grid,
+                             self.absorbed_old)
+        sed.add_contribution('nebular.absorption_young', sed.wavelength_grid,
+                             self.absorbed_young)
+
+
+# CreationModule to be returned by get_module
+Module = NebularEmission

pcigale/session/configuration.py

@@ -132,7 +132,7 @@ class Configuration(object):
             ["Order of the modules use for SED creation. Available modules:"] +
             ["SFH: sfh2exp, sfhdelayed, sfhfromfile, sfhperiodic"] +
             ["SSP: bc03, m2005"] +
-            ["Nebular emission: nebular"] +
+            ["Nebular emission: nebular, nebular_noemission"] +
             ["Dust attenuation: dustatt_calzleit, dustatt_powerlaw"] +
             ["Dust emission: casey2012, dale2014, dl2007, dl2014"] +
             ["AGN: dale2014, fritz2006"] +
@@ -219,7 +219,8 @@ class Configuration(object):
             self.config['sed_creation_modules'].comments[module_name] = [
                 creation_modules.get_module(module_name, blank=True).comments]
 
-        if 'nebular' not in self.config['creation_modules']:
+        if ('nebular' not in self.config['creation_modules'] and
+            'nebular_noemission' not in self.config['creation_modules']):
             print("WARNING: no nebular module selected. The Lyman continuum "
                   "is left untouched.")