extinction.odonnell94(wave, a_v, r_v, unit='aa', out=None)

O’Donnell (1994) extinction function.

Like Cardelli, Clayton, & Mathis (1989) [1] but using the O’Donnell (1994) [2] optical coefficients between 3030 A and 9091 A.

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.

Extinction in magnitudes at each input wavelength.


This function matches the Goddard IDL astrolib routine CCM_UNRED. From the documentation for that routine:

  1. The CCM curve shows good agreement with the Savage & Mathis (1979) [3] ultraviolet curve shortward of 1400 A, but is probably preferable between 1200 and 1400 A.
  2. Curve is extrapolated between 912 and 1000 A as suggested by Longo et al. (1989) [4]
  3. Valencic et al. (2004) [5] revise the ultraviolet CCM curve (3.3 – 8.0 um^-1). But since their revised curve does not connect smoothly with longer and shorter wavelengths, it is not included here.


[1]Cardelli, J. A., Clayton, G. C., & Mathis, J. S. 1989, ApJ, 345, 245
[2]O’Donnell, J. E. 1994, ApJ, 422, 158O
[3]Savage & Mathis 1979, ARA&A, 17, 73
[4]Longo et al. 1989, ApJ, 339,474
[5]Valencic et al. 2004, ApJ, 616, 912