Deriving Cube Moments¶
The Moments
class returns moment arrays as well as their errors for use with 2D statistics in the package. Moments are derived using spectral-cube. Definitions for the moments are also available in the spectral-cube documentation.
Basic Use¶
Moments are easily returned in the expected form for the statistics with Moments
. This class takes a FITS file of a spectral-line cube as input and creates moment arrays (zeroth, first, and line width) with their respective uncertainties.:
>>> from turbustat.moments import Moments
>>> # Load in the cube "test.fits"
>>> mm = Moments("test.fits")
>>> mm.make_moments()
>>> mm.make_moment_errors()
>>> output_dict = mm.to_dict()
output_dict
is a dictionary that contains keys for the cube and moments. The moment keys contain a list of the moment and its error map.
The moments can also be saved to FITS files. The to_fits
function saves FITS files of each moment. The input to the function is the prefix to use in the filenames:
>>> mm.to_fits("test")
This will produce three FITS files: test_moment0.fits
, test_centroid.fits
, test_linewidth.fits
for the zeroth, first, and square-root of the second moments, respectively. These FITS files will contain two extensions, the first with the moment map and the second with the uncertainty map for that moment.