SPLAT Summer 2003 pictures

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SPLAT Summer 2003 pictures

In this release SPLAT has become part of the Starlink Java Collection and is now released under the GPL.

The major changes to SPLAT in this release are:

  • Facilities to view and edit spectra in a table, with undo support.
  • The incorporation of a set of standard line identification catalogues for optical, IR and sub-millimetre.
  • Full support for spectral coordinate systems.
  • A new toolbox for filtering and smoothing spectra.

Other changes include the ability to delete as well as extract parts of spectra, to specify the types of spectra when the file extension is not one of the standard types and to drag-and-drop spectra from the global to plots.

The spectral editor

This figure shows SPLAT editing the data of a spectrum with a bad skyline subtraction. The bad values have been replaced with zero.

In addition to direct editing of individual values you can also use an algebraic expression to transform all the values of a column. It is also possible to add noise or generate a error column, add model lines and red or blue shift coordinates, as well as insert and delete rows. All changes are undo and re-doable and are immediately displayed in any views of the spectrum being changed.

Standard line catalogues

This figure shows SPLAT displaying a galaxy spectrum together with optical emission lines loaded from a standard catalogue. Note that the lines have been transformed to the rest frame of the galaxy.

As well as optical there are also IR and sub-millimetre wavebands catalogues, but, you can also import external catalogues using a standard text format.

Spectral coordinates

In this release SPLAT now makes use of the new SpecFrame and SpecMap provided by the Starlink AST library. This means that it is now possible to fully describe the spectral coordinate systems of all your spectra. This information can be added by you using a new SPLAT toolbox or derived from your data's standard encoding (FITS paper III or NDF WCS).

The main coordinate system types supported are, wavelength, frequency, energy and velocity. Which can be qualified by their units (angstroms, milli/nano/micro metres, Joules, ergs, electron volts, mega/kilo/giga hertz, metres/kilometres per second etc.) and the two associated systems of rest frame (i.e. where the observations were made and of what).

This information can be used to align spectra and line identifications automatically and perform operations like change of rest frame (say from topocentric to heliocentric, or centre

The figure displaying line identifications was produced by aligning a spectrum at rest with the source (i.e. as if the standards were observed alongside the galaxy) to one taken at a telescope on the Earth (the galaxy observation).

The next figures show an X-ray spectrum displayed in various coordinate systems. This was all created from the same data.

Smoothing and filtering

In this release SPLAT has now various smoothing filters added. These are:

  • Average - take the running average value over a number of positions.
  • Median - take the running median value over a number of positions.
  • Profile - smooth the values using a profile matched to typical line shapes, Gaussian, Lorentzian and Voigt.
  • Spectrum - smooth the values using a profile defined in another spectrum (allows you to create kernels that match some shape, rather than just the standard profiles).
  • Wavelet - use various wavelet filters to convert the spectrum into multiresolution coefficients, removing a fraction of the coefficients, thus "denoising" the spectrum.

Questions or comments to: p.w.draper@durham.ac.uk.

Copyright © 2005 Central Laboratory of the Research Councils
Copyright © 2006 Particle Physics and Astronomy Research Council
Copyright © 2008-2009 Science and Technlogy Facilities Council
Copyright © 2009-2013 Peter W. Draper
Last modified: 02-Jun-2016
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