Skip to main content

The NASA/GSFC network is currently experiencing intermittent issues that affect our services. We are working on it and apologize for the inconvenience.
The offline tool hark (also on github) can be used to find and download data from the cloud.

Xspec Home Page

next up previous contents
Next: method Up: Setting Commands Previous: abund   Contents


cosmo

set the cosmology

Set the cosmology used (i.e., $H_0$, $q_0$, and $\Lambda_0$).

Syntax: cosmo <$H_0$><$q_0$><$\Lambda_0$>

where <$H_0$> is the Hubble constant in km/s/Mpc, <$q_0$> is the deceleration parameter, and <$\Lambda_0$> is the cosmological constant. If the cosmological constant is non-zero then at present XSPEC requires that the universe is flat. In this case the value of <$q_0$> will be ignored and XSPEC will assume that $\Omega_{matter}\geq 1-\Lambda_0$. The default values are <$H_0$> = 70, <$q_0$> = 0.0, and <$\Lambda_0$> = 0.73

Examples:

XSPEC12>cosmo 100
// Set <$H_0$>= 100 km/s/Mpc
XSPEC12>cosmo ,0
// Set <$q_0$>= 0
XSPEC12>cosmo „0.7
// Set a flat universe with <$\Lambda_0$>= 0.7