Data Federation Science Cases

This page has been created to collect together cases in which there are clear scientific requirements for data federations of one sort or another. I'll start by drafting a few, and reference others already existing elsewhere on the wiki. Other contributions welcome, just edit this page.

Identifying 1XMM Sources

The 1XMM catalogue was recently published, containing X-ray sources detected in the fields of view of the XMM-Newton X-ray observatory during roughly its first year of operation. The resulting table of 56711 sources and over 300 columns included information apparent cross-identifications with sources in a number of standard catalogues, produced by a pipeline at CDS (Strasbourg). However astronomers are likely to want to cross-match 1XMM with other catalogues, or to carry out some pre-selection before cross-matching, or to vary the spatial cross-match criteria themselves.

Find AGNs near to Bright Stars

An observer interested in spectra of Active Galactic Nuclei wanted to find which of them had a bright star nearby, so that it could act as a phase-correction reference for adaptive optics. The exact critera depend on the waveband of interest, but typically one might want a star brighter than 15th magnitude within 30 arcseconds of the AGN. Such instances could be found by matching a table of AGNs with a standard star catalogue, such as USNO, 2MASS, APM, or SSS.

Find Double Stars

Double stars are interesting since observations over a long period can establish their orbital parameters and many more of their physical characteristics, such as mass, than is possible for isolated stars. A list of probable double stars can be found by searching any large catalogue of stellar objects (such as USNO) and selecting pairs of objects of similar magnitude which are substantially closer to each other than the typical separation of such stars in that area of sky. Similarity of proper motions would also be a factor in identifying a close pair of stars as a candidate double. This corresponds to a self-join of a table using position as the main matching criterion, but perhaps with magnitude and proper motions also taken into account.

Find Brown Dwarf Stars

It should be possible to find nearby Brown Dwarfs by selecting for stars with a high proper motion and a strong red or infra-red excess. This would involve joining a catalogue with proper motion information (e.g. USNO but that may not be the best) with another one which contained values for infra-red magnitudes, for example 2MASS.

Your science cases go here...

Data Federation Use-Cases

Some existing use-cases on the wiki include:

• ResultMerge - merge results from queries of a number of different (but presumably similar) catalogues.
• CatalogueCrossMatch - spatial joins between object catalogues - includes references to papers which have done this.

Suggestions for more, or more details for these, are needed.

-- ClivePage - 09 Jul 2003