Models implemented by Luis C. Reyes (lreyes04@calpoly.edu) and Jim Chiang (jchiang@slac.stanford.edu)

Optical depth tables are obtained from the authors (via public websites when available or via private communication).

Typically the table lists tau in a grid according to redshift and energy.  Interpolation is used to calculate tau for 
any arbitrary redshift and energy within the range.

EBL model  0: Kneiske et al. "Best Fit" 2004 (A&A 413, 807-815)
EBL model  1: Primack, Bullock, Somerville 2005  (astro-ph 0502177)
EBL model  2: Kneiske et al. "High-UV" 2004 (A&A 413, 807, 815)
EBL model  3: Stecker, Malkan, and Scully 2006 (ApJ, 648, 774 and erratum: ApJ 658, 1392S (2007))
EBL model  4: Franceschini et al. 2008 (A&A, 487, 837)
EBL model  5: Finke et al. 2010 (ApJ. 712, 238)
EBL model  6: Deprecated (returns EBL model 13)
EBL model  7: Stecker, Malkan, and Scully 2006 - "Fast Evolution" (ApJ, 648, 774)
EBL model  8: Salamon & Stecker 1998 - "with Metallicity Correction" (ApJ, 493, 547) 
EBL model  9: Generic (analytical) EBL model by J. Finke
EBL model 10: Dominguez et al. 2011 (MNRAS, 410, 2556)
EBL model 11: Kneiske & Dole 2010 (A&A, 515, 19)
EBL model 12: Kneiske & Dole 2010 - with CMB (A&A, 515, 19)
EBL model 13: Gilmore et al. 2010 (MNRAS, 399, 1694)
EBL model 14: Gilmore et al. 2012 - "Fiducial" (MNRAS, 422, 3189)
EBL model 15: Gilmore et al. 2012 - "Fixed" (MNRAS, 422, 3189)
EBL model 16: Scully et al. 2014 - "Low Opacity" (ApJ, 784, 138)
EBL model 17: Scully et al. 2014 - "High Opacity" (ApJ, 784, 138)
EBL model 18: Inoue et al. 2013 (ApJ, 768, 197)
EBL model 19: Helgason & Kashlinsky 2012 (ApJ, 758, 13)
