The inputs to CosmicCalculator can be specified with the following options:
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.
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 \(z\approx v/c\).
Current expansion rate (in km sec\(^{-1}\) Mpc\(^{-1}\)).
Cosmological constant density divided by the critical density in the current Universe (\(\Omega_{\Lambda,0}\)).
Matter (including massive neutrinos) density divided by the critical density in the current Universe (\(\Omega_{m,0}\)).
Radiation density divided by the critical density in the current Universe (\(\Omega_{r,0}\)).
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
JavaScript license information
GNU Astronomy Utilities 0.22 manual, February 2024.