ADASS XXXI

CASSIS and Aladin interfaced for a VO-compliant spectral data cube analysis tool

J.M Glorian, P. Fernique, T.Boch, M.Boiziot, F.Bonnarel, C.Bot, S.Bottinelli, E.Caux, A.Coutens, M.Louys, C.Vastel

Spectral cubes are becoming usual data products in astronomy. This is true in various spectral domains due to the high rate data production of large projects such as MUSE in optical, LOFAR, ALMA, VLA, NOEMA or ASKAP in radio astronomy, or Chandra and XMM in Xray. And this is only a hint of what will happen with the emergence of SKA or other Petascale projects in a near future. These cubes are generally on line and easy to be found and accessed due to the great number of VO services which distribute them. Efficient Display and Analysis of such spectral cubes is a big challenge.

In this context the CASSIS team at IRAP (http://cassis.irap.omp.eu) and the Aladin team at CDS (https://aladin.u-strasbg.fr/) decided to work together on the combination of their VO applications in order to create a tool able to explore both spatial and spectral dimensions of the cubes.

CASSIS is a java tool able to discover spectra in remote services via the SSAP protocol and analyse them. It provides functionalities such as spectrum display, spectral line identification, prediction of spectra from any telescope, comparison of spectra with various models and determination of the physical parameters of the sources.

Aladin is also a java tool able to discover images and cubes and display them (either in standard bitmap format or in the IVOA HiPS format (https://www.ivoa.net/documents/HiPS/) and catalogs available in the Virtual Observatory landscape. It allows transformation, overlays and comparison of data. Data discovery makes use of specific VO features such as MOCs (https://www.ivoa.net/documents/MOC/20210324/index.html) both in spatial and time dimension.

The focus demo will show how the two Desktop applications have been extended by a common dedicated interface in such a way that they behave together like a spectral cube analysis tool. For example CASSIS can analyse a spectrum built on the fly by Aladin after hand selection and combination of voxels in a specific area of a spectral cube. Reversely CASSIS allows to select spectral ranges on such spectra and ask Aladin to display 2D images combining the corresponding spectral planes in the cube.

The tool can work both on local data available on the user's disk or on cubes discovered via the VO registry and within VO services. We will demonstrate both modes.

More sophisticated developments will occur in the future and will be announced at the end of the demo.