GNU Astronomy Utilities

9.1.3 Invoking CosmicCalculator

CosmicCalculator will calculate cosmological variables based on the input parameters. The executable name is astcosmiccal with the following general template

$ astcosmiccal [OPTION...] ...

One line examples:

## Print basic cosmological properties at redshift 2.5:
$ astcosmiccal -z2.5

## Only print Comoving volume over 4pi stradian to z (Mpc^3):
$ astcosmiccal --redshift=0.8 --volume

## Print redshift and age of universe when Lyman-alpha line is
## at 6000 angstrom (another way to specify redshift).
$ astcosmiccal --obsline=Ly-alpha,6000 --age

## Print luminosity distance, angular diameter distance and age
## of universe in one row at redshift 0.4
$ astcosmiccal -z0.4 -LAg

## Assume Lambda and matter density of 0.7 and 0.3 and print
## basic cosmological parameters for redshift 2.1:
$ astcosmiccal -l0.7 -m0.3 -z2.1

## Print wavelength of all pre-defined spectral lines when
## Lyman-alpha is observed at 4000 Angstroms.
$ astcosmiccal --obsline=Ly-alpha,4000 --listlinesatz

The input parameters (current matter density, etc.) can be given as command-line options or in the configuration files, see Configuration files. For a definition of the different parameters, please see the sections prior to this. If no redshift is given, CosmicCalculator will just print its input parameters and abort. For a full list of the input options, please see CosmicCalculator input options.

Without any particular output requested (and only a given redshift), CosmicCalculator will print all basic cosmological calculations (one per line) with some explanations before each. This can be good when you want a general feeling of the conditions at a specific redshift. Alternatively, if any specific calculation(s) are requested (its possible to call more than one), only the requested value(s) will be calculated and printed with one character space between them. In this case, no description or units will be printed. See CosmicCalculator basic cosmology calculations for the full list of these options along with some explanations how when/how they can be useful.

Another common operation in observational cosmology is dealing with spectral lines at different redshifts. CosmicCalculator also has features to help in such situations, please see CosmicCalculator spectral line calculations.