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GAIA
GAIA
GAIA (Graphical Astronomy and Image Analysis Tool) is a
tool to analyse and display 2 and 3-dimensional data.
Full information about this tool can be obtained from the
GAIA manual
and the additional section about GAIA-3d.
It can be started by typing:
> gaia filename.sdf
Some features are not yet well explained in the manuals. These are discussed
below (figures will be added later).
Note that some more detailed help than in the manual is available
by clicking in the "Starlink GAIA::Skycat" window on Help --> Help topics index, or
in the "Display Image sections of a cube" window on Help --> On window ... (in the upper right hand corner).
In case of problems starting up GAIA, sometimes it helps to remove the
directory $home/.skycat
Baseline removal
GAIA can be used to remove baselines from all spectra in a cube. The same order
and velocity range will be used for all spectra.
1. Click in the "Display image sections of a cube" window on Baseline.
2. Click on a position in the map where there is a strong line to extract the
spectrum (will appear in a GAIA: Spectral plot window) to identify the
velocity range(s) without line. One can click on Coords --> Kilometres-per-sec (radio) to change the scale from frequency to velocity, if necessary.
3. Click in the "Display image sections of a cube" window on Show limit on plot
and Enable as many velocity ranges as needed.
4. Choose the Order of fits either by typing it in the window or using the slider.
5. Do the same for Lower index and Upper index to choose the velocity range in the
spectrum where there is no line (and repeat for all ranges).
6. Click on Run (at the bottom).
<Back to
Contents>
Animations
One can make animations in GAIA showing the line intensity as a function of
velocity by clicking in the "Display image sections of a cube" window on
Animation after loading a data cube into GAIA.
Clicking on a pixel will show
the spectrum at that position.
The velocity range used in the animation can
be selected by clicking on Show limits on plot and then changing the Lower
index and Upper index.
The animation is started by clicking on Start.
There are several
Looping options.
The animation will be saved in a file GaiaAnimation.gif
when clicking Capture on.
One can add graphics (e.g. coordinates) in the
usual way via the main GAIA window by clicking on Image-Analysis -->
Overlay axes grid.
Below is an example of an animation showing a 12CO(3-2)
jiggle map of CRL2688 (reload this webpage to view it again).
Displaying the variance array
After loading a cube into GAIA one can plot its variance array by
selecting in the "Display Image sections of a cube" window Options --> Data component --> Variance
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