etau_madau¶
-
synphot.reddening.
etau_madau
(wave, z, **kwargs)[source]¶ Madau 1995 extinction for a galaxy at given redshift. This is the Lyman-alpha prescription from the photo-z code BPZ.
The Lyman-alpha forest approximately has an effective “throughput” which is a function of redshift and rest-frame wavelength. One would multiply the SEDs by this factor before passing it through an instrument filter.
This approximation is from Footnote 3 of Madau et al. (1995). This is claimed accurate to 5%. The scatter in this factor (due to different lines of sight) is huge, as shown in Madau’s Fig. 3 (top panel); The figure’s bottom panel shows a redshifted version of the “exact” prescription.
Parameters: - wave : array-like or
Quantity
Redshifted wavelength values. Non-redshifted wavelength is
wave / (1 + z)
.- z : number
Redshift.
- kwargs : dict
Equivalencies for unit conversion, see
validate_quantity()
.
Returns: - extcurve :
ExtinctionCurve
Extinction curve to apply to the redshifted spectrum.
- wave : array-like or