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edge, zedge: absorption edge

The edge model is absorption edge, given by

$\displaystyle M(E) = \begin{array}{ll} 1 & E \leq E_c\\ [.2cm]exp\left[-D(E/E_c)^{-3}\right] & E \geq E_c \end{array}$
where:

par1=$E_c$ threshold energy
par2=$D$ absorption depth at the threshold

The zedge model given by

$\displaystyle M(E) = \begin{array}{ll} 1 & E < E_c\\ [.2cm]exp\left(-D\left[E(1+z)/E_c\right]^3\right) & E > E_c \end{array}$
allows a redshift z where:

par1=$E_c$ threshold energy
par2=$D$ absorption depth at the threshold
par3=z redshift