4.1.32. Reds: redshift model

This multiplicative model applies a redshift to an arbitrary additive component. If a photon is emitted at energy , the redshift model will put it at energy . In addition, a time dilatation correction is applied such that the spectrum (expressed as photons/s per bin) is divided by .

However, it is necessary to distinguish two different cases:

Case 1 (flag=0): In this case, the time dilatation correction described above is applied to the spectrum, which makes this the (default) option to be used for cosmological redshifts.

Case 2 (flag=1): By setting this flag, the time dilatation correction to the flux is not applied. This is used for a redshift caused by motion away from us. It should be used for any velocity fields other than the Hubble flow. Make sure that you limit z to a range -1<z<1 to remain within physical limits.

Warning

Note that this component should be used in tandem with the distance command (Distance: set the source distance) to take into account the cosmological redshift and its influence on the flux completely.

The parameters of the model are:

z : Redshift . Default value: 0. Dimensionless. Redshifts are positive, blueshifts negative.

flag : Flag: 0 (cosmological redshift) or 1 (velocity redshift). Default value: 0.