Synopsis
Set the cosmological parameters used by X-Spec models.
Syntax
set_xscosmo(h0, q0, l0)
Description
Set the cosmological parameters (H_0, q_0, lambda_0) used by X-Spec. It is equivalent to the X-Spec cosmo command [1] . The default values are h0=70, q0=0, and l0=0.73
Example
>>> set_xscosmo(73, 0, 0.73)
PARAMETERS
The parameters for this function are:
Parameter | Type information | Definition |
---|---|---|
h0 | number | The Hubble constant in km/s/Mpc. |
q0 | number | The deceleration parameter. |
l0 | number | The cosmological constant. If this is non-zero then the q0 parameter is ignored and the Universe is assumed to be flat. |
References
- [1] https://heasarc.gsfc.nasa.gov/xanadu/xspec/manual/XScosmo.html Note that this may refer to a newer version than the compiled version used by Sherpa; use `get_xsversion` to check.
XSPEC version
CIAO 4.17 comes with support for version 12.14.0k of the XSPEC models. This can be checked with the following:
% python -c 'from sherpa.astro import xspec; print(xspec.get_xsversion())' 12.14.0k
Bugs
See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.
See Also
- modeling
- get_xscosmo