CALZ_UNRED

     Deredden a galaxy spectrum using the Calzetti et al. (2000) recipe

     Calzetti et al.  (2000, ApJ 533, 682) developed a recipe for dereddening
     the spectra of galaxies where massive stars dominate the radiation output,
     valid between 0.12 to 2.2 microns.     (CALZ_UNRED extrapolates between
     0.12 and 0.0912 microns.)

     CALZ_UNRED, wave, flux, ebv, [ funred, R_V = ]

      WAVE - wavelength vector (Angstroms)
      FLUX - calibrated flux vector, same number of elements as WAVE
               If only 3 parameters are supplied, then this vector will
               updated on output to contain the dereddened flux.
      EBV  - color excess E(B-V), scalar.  If a negative EBV is supplied,
               then fluxes will be reddened rather than deredenned.
               Note that the supplied color excess should be that derived for
               the stellar  continuum, EBV(stars), which is related to the
               reddening derived from the gas, EBV(gas), via the Balmer
               decrement by EBV(stars) = 0.44*EBV(gas)

      FUNRED - unreddened flux vector, same units and number of elements
               as FLUX.   FUNRED values will be zeroed outside valid domain
               Calz_unred (0.0912 - 2.2 microns).

       R_V - Ratio of total to selective extinction, default = 4.05.
             Calzetti et al. (2000) estimate R_V = 4.05 +/- 0.80 from optical
             -IR observations of 4 starbursts.

       Estimate how a flat galaxy spectrum (in wavelength) between 1200 A
       and 3200 A is altered by a reddening of E(B-V) = 0.1.
       IDL> w = 1200 + findgen(40)*50      ;Create a wavelength vector
       IDL> f = w*0 + 1                    ;Create a "flat" flux vector
       IDL> calz_unred, w, f, -0.1, fnew  ;Redden (negative E(B-V)) flux vector
       IDL> plot,w,fnew

       Use the 4 parameter calling sequence if you wish to save the
               original flux vector.

      POLY()

       Written   W. Landsman        Raytheon  ITSS   December, 2000

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