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

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–1 Mpc–1, <q_0> is the deceleration parameter, and <lambda_0>is the cosmological constant. If the cosmological constant is non-zerothen 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 >= 1-lambda_0. The default values are <H_0> = 50, <q_0> = 0.5, and <lambda_0> = 0.



XSPEC12> cosmo 100

// Set <H_0> = 100 kms^-1 Mpc^-1

XSPEC12> cosmo ,0

// Set <q_0> = 0

XSPEC12> cosmo ,,0.7

// Set a flat universe with <lambda_0> = 0.7