DynSpec

Creates dynamic spectra given a list of source directions by phase shifting the observation MS to the directions of interest and averaging over all baselines.

The step supports subtraction of sources before measuring the spectrum, either by subtracting already predicted model visibilities or using an internal H5ParmPredict step. The subtracted sky model and the measured sources should currently not overlap, i.e., it is assumed that measured sources are not in the sky model given to the H5ParmPredict substep.

inputs

type

type:

string

doc:

Case-insensitive step type; must be ‘dynspec’.

applybeam.*

doc:

ApplyBeam sub-step, to apply the beam in the direction of each source in sourcelist, before measuring the spectrogram. Note that if you’re using this sub-step, you might want to set updateweights to True, to apply proper weighting to each pixel.

applycal.*

doc:

ApplyCal sub-step. For each source provided by sourcelist, calibration solutions (closest to the provided source direction) are applied. Requires at least the calibration solutions (stored as H5Parm) and the type(s) of correction(s). The sub-step will be used if dynspec.applycal.parmdb is set.

beamcorrection

type:

boolean?

default:

True

doc:

Whether to apply beam corrections in the direction of each of the sources. By default the full beam (element beam and array factor) is applied, with the direction set by the directions provided by sourcelist. More tuning options are available via dynspec.applybeam.*.

fitsprefix

type:

string?

doc:

Filename prefix for the spectra written to disk in the FITS file format. The filename follows the pattern <prefix>-<source name>-dynspec.fits. The source name is read from the file specified by the sourcelist parameter.

h5parmpredict.*

doc:

H5ParmPredict sub-step. Requires at least a sky-model and calibration solutions to subtract predicted foreground sources. This is an alternative to subtraction with subtractmodelcolumn. Note that one of these options can be used!

sourcelist

type:

string

doc:

Name of the file containing a list of sources, .e.g., sources.skymodel (the filename should always end with with .skymodel or .txt). For each of these sources a dynamic spectrum with axes time, frequency and stokes parameter (I, Q, U, and V) will be created.

The source list needs to be defined using the familar sky-model text format. For example:

FORMAT = Name, Ra, Dec source_1, 02:00:00, -30.00.00 source_2, 00:10:00, +30.50.00

subtractmodelcolumn

type:

string?

doc:

Name of the MS column with foreground visibilities. These will be subtracted from the data before determining the dynamic spectrum.