WP-A5.2: X-ray pilot - Association techniques

(WPM: Watson - Staff: Watson, 0.05 FTE; Page, 0.10 FTE; Mann, 0.10 FTE; McMahon, 0.05 FTE)

This pilot identifies issues relating to the association of objects in different databases, using the specific example of determining optical counterparts of sources detected by XMM-Newton, thereby producing the federation of an XMM-Newton catalogue and optical catalogues covering the same fields. Since its launch in December 1999, XMM-Newton has observed more than 700 fields, detecting in excess of 50,000 sources. The first XMM-Newton source catalogue is being constructed by the XMM-Newton Survey Science Centre (SSC), and is due for public release in September 2002 - but prototype versions will be available for use in this pilot before then.

Example Science Case:

A scientist wishes to determine the variation of some X-ray hardness ratio as a function of X-ray flux and optical/near-infrared colour, to constrain models for the properties of the population of obscured AGN. To do this requires the association of objects in X-ray and optical/near-infrared catalogues, followed by the selection of subsamples of associated sources on the basis of X-ray properties.

Objectives:

• To produce a federation of optical and X-ray datasets in a significant number (several hundred) XMM-Newton fields, which can be used for scientific analysis.
• To assess the requirements for performing, within the VO, associations between catalogues of objects detected in different wavebands.

Inputs:

• A prototype version of the first XMM-Newton source catalogue to be released by the SSC.
• Object catalogues derived from optical data in the same fields as the XMM-Newton observations included in the X-ray catalogue.

Outputs:

• Associations test bed.
• Feedback on prototype system from test users.
• Inputs of requirements to WP-A1.
• Inputs of implementation issues to WP-A2, WP-A3, WP-A4 and WP-A9.
• Inputs to the development of the Phase B plan.

Tasks:

• 5.2.0 Design and requirements
  • Decide selection criteria for inclusion of XMM-Newton fields in test bed X-ray catalogue.
  • Prioritise optical catalogues: trade-off between depth and area - INT-WFC data are much deeper than SuperCOSMOS data, but cover a restricted area (only ~100 XMM-Newton fields).
  • Decide whether to put information relating to optical counterparts into the X-ray catalogue, or just insert into it some sort of links to the optical data.
  • Obtain user input as to what metadata describing the association procedure and results should be made available with the catalogue of associated sources.

• 5.2.1 Prepare optical data for fields covered by test bed catalogue
  • Decide on storage method(s) for optical data - in DBMS or in flat file system
  • Collect INT-WFC object catalogues from Cambridge, SuperCOSMOS object catalogues from Edinburgh, and store in chosen form.

• 5.2.2 Interface to prototype SSC catalogue
  • Develop interface to prototype of SSC catalogue: both for reading the X-ray source information required for association procedure, and for writing information relating to optical counterparts, when the association procedure has been run.

• 5.2.3 Association methods
  • Decide on association method(s) to be used in production of test bed catalogue.
  • Develop software to perform association procedure and run it on test bed catalogue.

• 5.2.4 Evaluate testbed implementation
  • Allow test users to study optical/X-ray properties of source catalogue.
  • Gather inputs from developers and users.
  • Produce a technical note on the lessons learnt.
  • Provide inputs to the Phase-B plan.

-- BobMann - 26 Feb 2002