extinction.ccm89¶
-
extinction.
ccm89
(wave, a_v, r_v, unit='aa', out=None)¶ Cardelli, Clayton & Mathis (1989) extinction function.
The parameters given in the original paper [1] are used. The claimed validity is 1250 Angstroms to 3.3 microns.
Parameters: - wave : numpy.ndarray (1-d)
Wavelengths or wavenumbers.
- a_v : float
Scaling parameter, A_V: extinction in magnitudes at characteristic V band wavelength.
- r_v : float
Ratio of total to selective extinction, A_V / E(B-V).
- unit : {‘aa’, ‘invum’}, optional
Unit of wave: ‘aa’ (Angstroms) or ‘invum’ (inverse microns).
- out : np.ndarray, optional
If specified, store output values in this array.
Returns: - Extinction in magnitudes at each input wavelength.
Notes
In Cardelli, Clayton & Mathis (1989) the mean R_V-dependent extinction law, is parameterized as
\[<A(\lambda)/A_V> = a(x) + b(x) / R_V\]where the coefficients a(x) and b(x) are functions of wavelength. At a wavelength of approximately 5494.5 angstroms (a characteristic wavelength for the V band), a(x) = 1 and b(x) = 0, so that A(5494.5 angstroms) = A_V. This function returns
\[A(\lambda) = A_V (a(x) + b(x) / R_V)\]References
[1] Cardelli, J. A., Clayton, G. C., & Mathis, J. S. 1989, ApJ, 345, 245