Selection: field, spw, selectdata, intent, and observation

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4.4.1.2 Selection: field, spw, selectdata, intent, and observation

Selection is controlled by the parameters:

field        =         ’’   #   field names or index of calibrators: ’’==>all
spw          =         ’’   #   spectral window:channels: ’’==>all
intent       =         ’’   #  Select observing intent
selectdata   =      False   #   Other data selection parameters

Field and spectral window selection are so often used, that we have made these standard parameters field and spw respectively. intent is the scan intent that was specified when the observations were set up. They typically describe what was intended with a specific scan, i.e. a flux or phase calibration, a bandpass, a pointing, an observation of your target, or something else or a combination. The format for the scan intents of your observations are listed in the logger when you run listobs. Minimum matching with wildcards will work, like ’*BANDPASS*’. This is especially useful when multiple intents are attached to scans. Fibally, observation is an identifier to distinguish between different observing runs, mainly used for ALMA.

The selectdata parameter expands as usual, uncovering other selection sub-parameters:

selectdata          =       True        #  data selection parameters
     field          =         ’’        #  field names or field index numbers (blank for all)
     spw            =         ’’        #  spectral windows:channels (blank for all)
     timerange      =         ’’        #  time range (blank for all)
     uvrange        =         ’’        #  uv range (blank for all)
     antenna        =         ’’        #  antenna/baselines (blank for all)
     scan           =         ’’        #  scan numbers (blank for all)
     correlation    =         ’’        #  correlations (blank for all)
     array          =         ’’        #  (sub)array numbers (blank for all)
     observation    =         ’’        #  Select by observation ID(s)
     msselect       =         ’’        #  MS selection (blank for all)

Note that if selectdata=False these parameters are not used when the task is executed, even if set underneath.

The most common selectdata parameter to use is uvrange, which can be used to exclude longer baselines if the calibrator is resolved, or short baselines of the calibrator contains extended flux not accounted for in the model (e.g. § 4.3.4.1).

See § 2.3 for more on the selection parameters.

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