** Mean Intensity of the Near Infrared Background for SFR=1Msun/Mpc^3/year **
This version assumes Salpeter's initial mass function (IMF) and metal-free
(popIII) stars. 

December 28, 2010: E.Komatsu
Ref: Fernandez & Komatsu, ApJ, 646, 703 (2006)

This code calculates the mean intensity of the near infrared background (NIRB)
using the method of Fernandez&Komatsu, for a constant star formation rate (SFR)
of 1 Msun/Mpc^3/year.

The mean intensity is given by

I_nu = (c/fourpi) int_{zend}^{zstart} dz p[(1+z)nu,z]/H(z)/(1+z),

where the comoving volume emissivity, p(nu,z), is given by

p(nu,z) = SFR*c^2*[sum_i <epsilon_i>(nu)]

Here, <epsilon_i>(nu) is the "radiative efficiency", which gives 
a ratio of the mass-weighted average of radiative energy of a radiation
process i (where i=free-free, free-bound, stellar, Lyman-alpha, two-photon)
to the stellar rest-mass energy, in a unit frequency interval.

The radiative efficiency is calculated from

<epsilon_i>(nu) = (1/mstar) int_m1^m2 dm m*f(m)*[ L_i(nu,m)tau(m)/(m c^2) ],

where mstar [=int dm m*f(m)] is the mean stellar mass, f(m) is the initial
mass spectrum, and L_i(nu,m) is the luminosity of each radiation process 
in a unit frequency interval.

- To compile and use the program, edit Makefile and simply "make"
- It will generate an executable called "compute_nuinu"
- Running it will yield two files: 

"hnu_nu_ff_fb_star_lya_2g_nuInu.txt" contains nu*Inu
1st column: h*nu [eV]
2nd column: nu   [Hz]
3rd column: free-free   [nW/m^2/str]
4th column: free-bound  [nW/m^2/str]
5th column: stellar     [nW/m^2/str]
6th column: Lyman-alpha [nW/m^2/str]
7th column: two-photon  [nW/m^2/str]

"hnu_nu_ff_fb_star_lya_2g_nuenu.txt" contains nu*<epsilon>. 
1st column: h*nu [eV]
2nd column: nu   [Hz]
3rd column: free-free   [dimensionless]
4th column: free-bound  [dimensionless]
5th column: stellar     [dimensionless]
6th column: Lyman-alpha [dimensionless]
7th column: two-photon  [dimensionless]