ScienceProblem: ClassifyXraySourcePopulation

PrimaryActor:

Research astronomer

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ScienceGoal:

To characterise the X-ray source population.

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DataSets:

Representative samples of X-ray sources, plus data in other wavebands - especially the optical/near-infrared, but others, in principle, too. Of the current major projects in this area, the XID programme run by the XMM-Newton Survey Science Centre is obtaining a lot of its own imaging and spectroscopic data, whereasClassX, led from HEASARC is more of a proto-VO project, seeking associations between existing databases - namely X-ray sources from the WGACAT database of ROSAT point sources, and optical/near-infrared sources from USNO-A2, 2MASS and GSC-II.

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ProblemDescription:

A major opportunity afforded by the VO will be the ability to undertake readily very large statistical analyses, such as taking a census of the properties of a particular class of objects. The past ten years has seen a huge expansion in the amount of data available on the X-ray sky, from the All-Sky Survey data from ROSAT, to the much deeper observations by Chandra and XMM-Newton, so it is appropriate to consider using the VO to undertake a census to characterise the properties of the X-ray source population, and thereby produce a classification of X-ray sources.

As described above, there are already two major projects of this sort underway: the XID programme being run on a representative set of XMM-Newton fields as they are observed, and ClassX, which is based on archival ROSAT data. At the core of both these projects is the probabilistic association of X-ray sources with optical/near-infrared objects, and the VO might hope to provide associations to observations in further bands, which might provide additional help in characterising and classifying the X-ray source population, and also to provide better tools for analysing the data collected by these two projects.

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CurrentSolution:

Two current solutions:

1. ClassX. This is a proto-VO project, aimed at find associations between X-ray point sources in the WGACAT database of ROSAT point sources, and optical/near-infrared sources from USNO-A2, 2MASS and GSC-II archives. Clearly, since it is a proto-VO project, it is also a prototype for the VOSolution to this problem.

1. XID. A project to obtain optical/near-infrared imaging and optical spectroscopy for a representative sample of XMM-Newton sources. Here the emphasis is on getting new data, rather than searching archives.

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VOSolution:

The VO is unlikely to improve substantially on the census of the X-ray source population that these two projects will provide, when taken together, since both have been designed to have statistical validity, through careful sample selection. The VO would, of course, offer users the ability to define different samples of X-ray sources using different sets of selection criteria, but these would likely be specialisations upon the general censuses undertaken by ClassX and XID.

However, the VO can extend these two projects in two important regards. Firstly, it can collate further data relating to the sources in the two survey, via cross-correlating their source lists with datasets in other wavebands - e.g. through application of UseCase GetFluxOrUpperLimitAtPosition. Secondly, and more importantly, the VO can provide the analysis tools required to extract the full scientific information contained in these two surveys - for example, by providing the data mining facilities (both hardware and associated hardware) required to investigate the multidimensional data spaces that they will span.

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Discussion:

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KeyReferences:

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GoodStyle: Please add comments below. This area should be used for refinement of the above document. If you want to ask questions or start a dialogue with the author, please use (or create) a topic in the Science Problems Forum. For other ScienceProblems, refer to the ScienceProblemList.
Author: Once the refinements here and comments in the forum die down, perhaps you could rewrite the problem, incorporating the comments and refinements.

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This case is being addressed in a limited manner by the AG pilot programme Astrogrid.WP-A5-2. Here the aim would be to extend the scope as more quality X-ray data becomes available. This should be an AstroGrid driver.

-- NicholasWalton - 17 Apr 2002

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-- BobMann - 12 Feb 2002