Description¶

A GalaxyParameters object gp is merely a glorified numpy.ndarray with convenience accessors and mutators :

Warning

the velocity_dispersion parameter is NOT the total dispersion. This parameter is akin to a turbulent term. It is added in quadrature to the dispersions due to the disk model and to the thickness. See Cresci et al. 2009, Genzel et al. 2011, and Bouche et al. 2015

You still can access the parameters like an indexed array

assert gp.x == gp[0]  # true
assert gp.y == gp[1]  # true
# ...
assert gp.sigma0 == gp[9]  # true

You may instantiate a GalaxyParameters object like so

from galpak import GalaxyParameters

gp = GalaxyParameters(z=0.65)
gp.x = 5.
assert gp.z == 0.65       # true
assert gp.x == 5.         # true

Warning

An undefined value in GalaxyParameters will be nan, not None

assert math.isnan(gp.pa)  # true
assert gp.pa is None      # false

Getting the Wavelength¶

The z attribute in a GalaxyParameter is in pixels, you may want the value in the physical unit specified in your Cube’s header.

To that effect, you may use the wavelength_of method of the HyperspectralCube:

from galpak import GalPaK3D
gk = GalPaK3D('my_muse_cube.fits')
gk.run_mcmc()

wavelength = gk.cube.wavelength_of(gk.galaxy.z)