zeus21.SED
==========

.. py:module:: zeus21.SED

.. autoapi-nested-parse::

   SEDs and Green's functions for first-galaxy emission models.

   Authors: zeus21 v2 collaboration - June 2026
       Emily Bregou ;
       Hector Afonso G. Cruz ;
       Sarah Libanore ;
       Julian B. Muñoz ;
       Yonny Sklansky ;
       Emilie Thélie ;
       Alessandra Venditti
   arXiv:2302.08506, arXiv:2306.09403, arXiv:2407.18294, Sklansky et al. (in prep)



Functions
---------

.. autoapisummary::

   zeus21.SED.SED_XRAY
   zeus21.SED.SED_LyA
   zeus21.SED.Greens_function_LUV
   zeus21.SED.Selection_Timescales_LUV
   zeus21.SED.Greens_function_LUV_Short
   zeus21.SED.Greens_function_LUV_Long
   zeus21.SED.Greens_function_LHa


Module Contents
---------------

.. py:function:: SED_XRAY(AstroParams, En, pop=0)

   X-ray SED for Pop II or Pop III sources.

   Normalized so that ∫_{E0}^{Emax} E · SED(E) dE = 1, i.e. E·SED is a
   power law with index alpha_xray. The function returns the *photon number*
   spectrum (divided by E at the end).

   The high-energy cutoff is intentionally omitted because photons redshift
   down into the <2 keV observing band.

   :param AstroParams: Must expose: alpha_xray, alpha_xray_III, E0_xray, Emax_xray_norm.
   :type AstroParams: object
   :param En: Photon energy in eV.
   :type En: float or array-like
   :param pop: Stellar population. 2 = Pop II, 3 = Pop III.
   :type pop: {2, 3}

   :returns: SED in units of eV⁻¹, same shape as En.
             Zero below E0_xray.
   :rtype: ndarray


.. py:function:: SED_LyA(nu_in, pop=0)

   Lyman-alpha continuum SED for Pop II or Pop III sources.

   A two-segment power law in frequency, joined at ν_LyB:
     • νLyA  ≤ ν < νLyB  : index indexbelow  (flatter)
     • νLyB  ≤ ν < νLyCont: index indexabove  (steeper)

   Normalized so that ∫_{νLyA}^{νLyCont} SED(ν) dν = 1 (photon number
   per unit frequency). Contrast with SED_XRAY, which normalizes E·SED.

   :param nu_in: Frequency in the same units as constants.freqLyA / freqLyCont.
   :type nu_in: float or array-like
   :param pop: Stellar population. Uses BL05 stellar spectra as reference.
               Pop II: amps = [0.68, 0.32], Pop III: amps = [0.56, 0.44].
   :type pop: {2, 3}

   :returns: SED value(s), same shape as nu_in. Zero outside [νLyA, νLyCont).
   :rtype: ndarray


.. py:function:: Greens_function_LUV(AstroParams, ageMyrin, Mhalos)

   UV luminosity Green's function for a 1 M☉/yr instantaneous burst at some time t.

   Convolve with SFR(t) to get L_UV(t):
       L_UV(t) = ∫ G_UV(t - t') · SFR(t') dt'

   The shape is a double-power-law in age (fast rise, slow decline) with a
   Gaussian bump at very young ages (~2–4 Myr) capturing the brief Wolf-Rayet
   and OB-supergiant phase. A Gaussian exponential cutoff suppresses
   contributions beyond ~650–1100 Myr depending on the SED model.

   :param AstroParams: Must choose SEDMODEL ∈ {'bagpipes', 'BPASS', 'BPASS_binaries'}.
   :type AstroParams: object
   :param ageMyrin: Stellar population age in Myr. A small offset (1e-4 Myr) is added
                    internally to avoid division by zero at age = 0.
   :type ageMyrin: float or array-like, shape (Nt,)
   :param Mhalos: Halo masses in M☉. Currently enter only through IMFZcorrection,
                  which is unity for UV (correction absorbed into ε*).
   :type Mhalos: array-like, shape (NMh,)

   :returns: Green's function in erg s⁻¹ M☉⁻¹.
   :rtype: ndarray, shape (NMh, Nt)


.. py:function:: Selection_Timescales_LUV(times, time1, time2)

   Returns the selection function from t1 to t2, to keep t1 < t < t2 smoothly


.. py:function:: Greens_function_LUV_Short(AstroParams, time, mass)

   Age in Myr, window in erg/s/Msun for the short timescale LUV window


.. py:function:: Greens_function_LUV_Long(AstroParams, time, mass)

   Age in Myr, window in erg/s/Msun for the long timescale LUV window


.. py:function:: Greens_function_LHa(AstroParams, ageMyrin, Mhalos)

   Hα luminosity Green's function for a 1 M☉/yr instantaneous burst at some past time t.

   Analogous to Greens_function_LUV but for the Hα recombination line.
   Hα traces ionizing photons and therefore falls off much faster with age
   (~few Myr vs. ~Gyr for UV). For BPASS_binaries there is a second component at ~20 Myr to account
   for delayed ionizing flux.

   The IMF/metallicity correction scales with halo mass as a power law,
   clamped to [0.1, 10] to prevent runaway corrections.


   :param AstroParams: Must expose: SEDMODEL, normLHa_ZIMF, alphanormLHa_ZIMF.
   :type AstroParams: object
   :param ageMyrin: Stellar population age in Myr.
   :type ageMyrin: float or array-like, shape (Nt,)
   :param Mhalos: Halo masses in M☉. Used in the IMF/Z mass-dependent correction.
   :type Mhalos: array-like, shape (NMh,)

   :returns: Green's function in erg s⁻¹ M☉⁻¹.
   :rtype: ndarray, shape (NMh, Nt)