IMAGING step

The IMAGING button/sub-panel will scan all spectral windows to identify whether they can be used to produce a Continuum or spectral line image.

Low resolution spectral windows, identified as those whose resolution is coarser than ALL%MINFRES will be used to produce continuum images, by filtering any detected spectral signature in the data before.

For High resolution spectral windows, identified as those whose resolution is better than ALL%MINFRES, data cubes will be produced.

In SPLIT Mode, if a Line Catalog is present, these high spectral resolution windows will be scanned for line identifications. For each spectral line in the current catalog(s) (defined by command CATALOG) that fall in a spectral window, a continuum-free UV table will be created, covering the velocity range specified by the user (by variable ALL%RANGE) around the line frequency. The naming convention is the following:

  original-molecule-I-X

where
- original is the name of the initial high resolution spectral window
- molecule is the name of the spectral line in the catalog
- I is a sequence number, incremented each time a new line is found from the same original UV table.
- X is a character code, equal to D if the line is suspected to be detected, and to U if not. When several lines are too close together, the D status may be incorrectly affected, but this is just a naming convention, not a strong result.

In addition an

  original-C

file that contains (presumably) line-free emission only is created for each original UV table.

The imaging results are stored in a specific sub-directory (./MAPS/ by default, controlled by all%maps). Only the Clean Component Table ( .cct) and Clean image ( .lmv-clean) files are written.

When no Line catalog is present, only 3 images are produced for each UV table: starting from the original name

  original-C       original-U    and   original-A

The ...-C contains (an estimate of) line-free emission, averaged over the bandwidth of the UV data. The ...-U is the continuum subtracted image, while in ...-A the pseudo-continuum image obtained after ...-C has been added back. The ...-A thus contains all the signal, and can be used to provide a better estimate of the continuum level using e.g. the MAP_CONTINUUM command.

Spectral resampling can be performed by appropriate setting of ALL%RANGE. If non zero, ALL%RANGE[3] indicates the desired spectral resolution. Furthermore, in the CATALOG case, ALL%RANGE[1:2], if non zero, specify the Min and Max velocities imaged around each spectral line.

In ALL mode, the behaviour is similar, but only the -C and -A products are created.

In CONTINUUM mode, line emission is assumed to be negligible, and only the -C continuum images are produced. Running the Pipeline in this mode first can be a quick way to evaluate the data content.