ScienceProblem: ComplexObjectIdentification

PrimaryActor

Astronomer

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ScienceGoal

To find counterparts or associated objects with a different appearance or location, for example an optically-bright galactic nucleus associated with widely separated radio jets.

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DataSets

See references - for the example above, typical radio objects are shown in An Atlas of DRAGNs and a search for the optical counterparts might be made in the HST archive and other catalogues containing compact extra-galactic objects.

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ProblemDescription:

Examples:

To match radio observations of DRAGNs (Double Radiosources Associated with Galactic Nuclei) with the nuclei. The DRAGNs contain radio lobes which may be many arcsec apart. The nucleus is compact (sub-arcsec) and may not be at the geometric centre between the mean positon of each lobe. Factors to consider (relating to the lobes and/or the core) include the direction of elongation of each radio lobe, and of any jets emanating from the candidate core, radio VLBI or spectral index measurements and X-ray images.

To identify the lensing object producing a lensed image with 2, 4 or many components or a ring, and compare candidate lenses with models derived from the properties of the lensed system. Multiple lenses are possible. The criteria include redshift, location and mass/energy distribution (determined from the optical morphology etc.).

To compare all observations of a star-forming region up to several arcmin in size, to (for example) distinguish between very massive hot YSOs, regions of advanced star and (proto-)planetary disc formation, and regions which are just starting to collapse (see StarFormingRegionStructure).

To measure the foreground electron screen(s) causing Faraday rotation of polarised emission from a background object (see GalacticMaserFaradayRotation).

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CurrentSolution:

Much painstaking searching of catalogues and the literature, with large search boxes, performing astrometric alignment. Drawing up successive shortlists of objects with suitable properties jusdged by different criteria. Possibly reducing data where the object of interest may be serendipitously located in the footprint of an unrelated target.

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VOSolution:^?

The user has to specify the criteria accurately but conditional searches could be made, for example using optical brightness and emission line properties and radio spectral index and VLBI detection to shortlist DRAGN cores in a large search box, and then using the lobe properties to confirm/reject the best candidate. Astrometric alignment and extracting mapped but archived data is performed automatically.

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KeyReferences:

(Extragalactic)

An Atlas of DRAGNs

Condon, J. J., Cotton, W. D., Greisen, E. W., Yin, Q. F., Perley, R. A., Taylor, G. B., & Broderick, J. J. 1998, The Astronomical Journal, Volume 115, Issue 5, pp. 1693-1716. The NRAO VLA Sky Survey

Becker, Robert H., White, Richard L., & Helfand, David J. 1995, Astrophysical Journal v.450, p.559 The FIRST Survey: Faint Images of the Radio Sky at Twenty Centimeters

Baker, Joanne C., Hunstead, Richard W., Kapahi, Vijay K., & Subrahmanya, C. R. 1999, The Astrophysical Journal Supplement Series, Volume 122, Issue 1, pp. 29-50. The Molonglo Reference Catalog 1 JY Radio Source Survey. IV. Optical Spectroscopy of a Complete Quasar Sample

Machalski, J., Jamrozy, M., & Zola, S. 2001, Astronomy and Astrophysics, v.371, p.445-469 (2001) The new sample of Giant radio sources. I. Radio imaging, optical identification and spectroscopy of selected candidates

Yang, Chen, Jin-Lin, Han, & Xiang-Tao, He 2001, Chinese Astronomy and Astrophysics, Volume 25, Issue 1, p. 6-22. Radio quasars identified from the NVSS catalogue

Colless, Matthew+ 2001, Monthly Notices of the Royal Astronomical Society, Volume 328, Issue 4, pp. 1039-1063. The 2dF Galaxy Redshift Survey: spectra and redshifts

Arnouts, S., Vandame, B., Benoist, C., Groenewegen, M. A. T., da Costa, L., Schirmer, M., Mignani, R. P., Slijkhuis, R., Hatziminaoglou, E., Hook, R., Madejsky, R., Rité, C., & Wicenec, A. 2001, Astronomy and Astrophysics, v.379, p.740-754 (2001) ESO imaging survey. Deep public survey: Multi-color optical data for the Chandra Deep Field South

Croom, S. M., Smith, R. J., Boyle, B. J., Shanks, T., Loaring, N. S., Miller, L., & Lewis, I. J. 2001, VizieR On-line Data Catalog: VII/223. Originally published in: 2001MNRAS.322L..29C The 2dF QSO Redshift Survey. V. The 10k catalogue (Croom+ 2001)

Corbin, Michael R., O'Neil, Earl, Thompson, Rodger I., Rieke, Marcia J., & Schneider, Glenn 2000, The Astronomical Journal, Volume 120, Issue 3, pp. 1209-1220. A Color Analysis of the NICMOS Parallel Image Archive

Zaggia, S., Hook, I., Mendez, R., da Costa, L., Olsen, L. F., Nonino, M., Wicenec, A., Benoist, C., Deul, E., Erben, T., Guarnieri, M. D., Hook, R., Prandoni, I., Scodeggio, M., Slijkhuis, R., & Wichmann, R. 1999, Astronomy and Astrophysics Supplement, v.137, p.75-81 ESO Imaging Survey. IV. Multicolor analysis of point-like objects toward the South Galactic Pole

Ratcliffe, A., Shanks, T., Parker, Q. A., Broadbent, A., Watson, F. G., Oates, A. P., Collins, C. A., & Fong, R. 1998, VizieR On-line Data Catalog: J/MNRAS/300/417. Originally published in: 1998MNRAS.300..417R Durham/UKST Galaxy Redshift Survey (Ratcliffe+, 1998)

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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 is probably a science driver for AG. Need to define the exact data sets that should be searched - e.g. can you start with optically selected AGN lists then check radio images?

-- NicholasWalton - 17 Apr 2002

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-- AnitaRichards - 04 Feb 2002