The inputs to CosmicCalculator can be specified with the following options:

`-z FLT``--redshift=FLT`The redshift of interest. There are two other ways that you can specify the target redshift: 1) Spectral lines and their observed wavelengths, see

`--obsline`. 2) Velocity, see`--velocity`. Hence this option cannot be called with`--obsline`or`--velocity`.`-y FLT``--velocity=FLT`Input velocity in km/s. The given value will be converted to redshift internally, and used in any subsequent calculation. This option is thus an alternative to

`--redshift`

or`--obsline`

, it cannot be used with them. The conversion will be done with the more general and accurate relativistic equation of \(1+z=\sqrt{(c+v)/(c-v)}\), not the simplified \(z\approx v/c\).`-H FLT``--H0=FLT`Current expansion rate (in km sec\(^{-1}\) Mpc\(^{-1}\)).

`-l FLT``--olambda=FLT`Cosmological constant density divided by the critical density in the current Universe (\(\Omega_{\Lambda,0}\)).

`-m FLT``--omatter=FLT`Matter (including massive neutrinos) density divided by the critical density in the current Universe (\(\Omega_{m,0}\)).

`-r FLT``--oradiation=FLT`Radiation density divided by the critical density in the current Universe (\(\Omega_{r,0}\)).

`-O STR/FLT,FLT`¶`--obsline=STR/FLT,FLT`-
Find the redshift to use in next steps based on the rest-frame and observed wavelengths of a line. This option is thus an alternative to

`--redshift`

or`--velocity`

, it cannot be used with them.The first argument identifies the line. It can be one of the standard names, or any rest-frame wavelength in Angstroms. The second argument is the observed wavelength of that line. For example,

`--obsline=Ly-alpha,6000`is the same as`--obsline=1215.64,6000`. Wavelengths are assumed to be in Angstroms by default (other units can be selected with`--lineunit`, see CosmicCalculator spectral line calculations).The list of pre-defined names for the lines in Gnuastro’s database is available by running

$ astcosmiccal --listlines

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GNU Astronomy Utilities 0.20 manual, April 2023.