msmoments

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8.2.1.19 msmoments

Keyword arguments:
infile -- Name of input MS data
        default: none; example: infile="OrionS_rawACSmod"
moments -- List of moments you would like to compute
        default: 0 (integrated spectrum);example: moments=[0,1]
        see list above
antenna -- antenna name or id that the user wants to compute moments
        default: ’’ (all antennae)
field -- field name or id that the user wants to compute moments
        default: ’’ (all fields)
spw -- spectral window id that the user wants to compute moments
        default: ’’ (all spectral windows)

includemask -- List of masks to include
        default: [-1] (include all channels); example=[2,100]
excludemask -- List of masks to exclude
        default: [-1] (don’t exclude channels); example=[100,200]
outfile -- Output MS file name (or root for multiple moments)
        default: ’’ (input+auto-determined suffix);example: outfile=’source_moment’
overwrite -- Overwrite existing output files
        default: false

Task msmoments computes moments from spectral data stored in MS. The task is defined in analogy with immoments task, so that you can calculate any moments that is available forimmoments task. Currently, the task only accepts MS with FLOAT_DATA column.

The spectral moment distributions at each row in input MS are determined. Input MS must have FLOAT_DATA column, i.e. autocorrelation data. See the cookbook and User Reference Manual for mathematical details.

The main control of the calculation is given by parameter moments:

moments=-1 - mean value of the spectrum
moments=0 - integrated value of the spectrum
moments=1 - intensity weighted coordinate;traditionally used to get ’velocity fields’
moments=2 - intensity weighted dispersion of the coordinate; traditionally used to get ”velocity dispersion”
moments=3 - median of I
moments=4 - median coordinate
moments=5 - standard deviation about the mean of the spectrum
moments=6 - root mean square of the spectrum
moments=7 - absolute mean deviation of the spectrum
moments=8 - maximum value of the spectrum
moments=9 - coordinate of the maximum value of the spectrum
moments=10 - minimum value of the spectrum
moments=11 - coordinate of the minimum value of the spectrum

Note that includemask and excludemask cannot set simultaneously.

Example for finding the 1-momment, intensity-weighted coordinate, often used for finding velocity fields.

msmoments( infile="mydata", moment=1, outfile="velocityfields" )

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