Absm: Morrison & McCammon absorption model

Absm: Morrison & McCammon absorption model#

This model calculates the transmission of neutral gas with cosmic abundances as published first by Morrison & McCammon (1983). It was a widely used model, but is now deprecated.

Warning

This is a deprecated model. For modeling the absorption of the interstellar medium (ISM), please use the Hot: collisional ionisation equilibrium absorption model in ISM mode instead of this one.

The following is useful to know when this model is applied:

  1. The location of the absorption edges is not always fully correct; this can be seen with high resolution grating spectra

  2. The model fails in the optical/UV band (i.e., it does not become transparent in the optical)

  3. No absorption lines are taken into account

  4. The abundances cannot be adjusted

The Morrison & McCammon model should only be used to compare with historic spectral fits. The Hot: collisional ionisation equilibrium absorption model model, set with a low temperature and in ISM mode provides much more detail and precision.

The parameters of the model are:

nh : Hydrogen column density in \(10^{28}\) \(\mathrm{m}^{-2}\). Default value: \(10^{-4}\) (corresponding to \(10^{24}\) \(\mathrm{m}^{-2}\), a typical value at low Galactic latitudes).
f : The covering factor of the absorber. Default value: 1 (full covering)

Recommended citation: Morrison & McCammon (1983).