Initial Conditions & Lookup Tables ================================== .. Cosmological Initial Conditions .. ------------------------------- .. .. .. .. .. .. .. The Halo Mass Function .. ---------------------- The Opacity of the Intergalactic Medium --------------------------------------- Solutions for the evolution of the cosmic X-ray background are greatly accelerated if one tabulates the IGM opacity, :math:`\tau_{\nu}(z, z^{\prime})`, ahead of time (see in Appendix C of `Haardt & Madau (1996) `_ for some discussion of this technique). *ARES* automatically looks in ``$ARES/input/optical_depth`` for :math:`\tau_{\nu}(z, z^{\prime})` lookup tables. The shape of the lookup table is defined by the redshift range being considered (set by the parameters ``first_light_redshift`` and ``final_redshift``), the number of redshift bins used to sample that interval, ``tau_redshift_bins``, the minimum and maximum photon energies (``pop_Emin`` and ``pop_Emax``), and the number of photon energies (determined iteratively from the redshift and energy intervals and the value of ``tau_redshift_bins``). By default, ares generates tables assuming the IGM is fully neutral, but that is not required. To make optical depth tables of your own, see ``$ARES/input/optical_depth/generate_optical_depth_tables.py``. See Section 3 of `Mirocha (2014) `_ for more discussion of this technique. Tables for ``mirocha2017``-like calculations ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To generate the table used for the calculations in `Mirocha, Furlanetto, & Sun (2017) `_, modify the following lines of ``$ARES/input/optical_depth/generate_optical_depth_tables.py``: :: zf, zi = (5, 50) Emin = 2e2 Emax = 3e4 Nz = [1e3] helium = 1 .. note :: You can run the ``generate_optical_depth_tables.py`` script in parallel via, e.g., ``mpirun -np 4 generate_optical_depth_tables.py``, so long as you have MPI and mpi4py installed. The set of parameters used for these calculations are described in the "Simulations" section of :doc:`param_bundles`.