ScienceProblem: QuasarHostGalaxiesBlackHoleMasses

PrimaryActor:

Research astronomer

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ScienceGoal:

To understand the place of the quasar phenomenon in galaxy evolution, through a study of the properties of quasar host galaxies and the build up of the mass of their black holes.

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DataSets:

A variety of X-ray, UV, optical, near-infrared and radio databases: the VO-related portion of this ScienceProblem is principally the selection of appropriate targets for future observations, rather than doing the science with archival data themselves.

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ProblemDescription:

Recent results (e.g. Kukula et al. 2001, McLure and Dunlop 2001) are starting to shed light on the relationship between the mass of an active galaxy's black hole and its spheroidal stellar component, and on the evolution of that relationship with redshift. The elucidation of this relationship is crucial for understanding how the quasar phenomenon fits into the wider picture of the galaxy formation and evolution, and is, therefore, a prime astrophysical question for the coming decade.

Complementary information relevant to this question can be obtained via imaging and spectroscopic studies. High-resolution imaging studies of quasar host galaxies can reveal their structural properties, and some information about the history of their stellar populations from broad-band colours, while spectroscopy can yield black hole mass estimates from the linewidths of nuclear emission lines.

Both of these approaches require the proximity of stars in the correct magnitude range: the deconvolution of imaging data to remove the quasar component and leave the emission quasar host ready for structural analysis requires a local star to provide an accurate description of the instrumental point spread function (PSF), while, increasingly, the large, ground-based telescopes required to obtain such imaging data and/or nuclear spectra for obscured AGN, will require reasonably bright stars to operate the adaptive optics systems crucial to these observations.

Thus, the target selection problem reduces to being able to ask questions like 'give me a list of quasars within distance D of a star within a certain magnitude range in a given band', while an extension to this would involve defining subsamples of the quasars so selected by imposing additional criteria on, say, the radio luminosity of the quasar, or its X-ray luminoity or variability.

Additionally, of course, one would also like to be able to find the subset of such quasars for which there already exists optical/near-IR spectra of the type/quality needed to yield the required black hole mass estimate, so that this problem can start to be addressed using archival data.

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CurrentSolution:

The current solution to the target selection problem involves searching through catalogues of known quasars, to find targets which lie within the required distance of a star of the magnitude appropriate to the proposed observation with a particular instrument. This is a very laborious process, and also may yield lists of candidates that are either incomplete or have unnecessary selection biases. Since one starts with a catalogue of known quasars, one is necessarily restricted to quasars satisfying the criteria that define that catalogue, which may not be appropriate to the new study. Also, by sticking to existing quasar catalogues, one is missing out on the (probably much larger number of) quasars that are included in large photometric catalogues, and could be selected by the application of appropriate search criteria.

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VOSolution:

The VO solution to this problem is to enable the user to define a set of quasar subsamples by a series of inequalities in multi-colour space, coupled to a proximity search on stars satisfying a magnitude constraint. To start tackling this problem using archival data would necessitate the additional ability to query spectroscopic archives for existing spectra of the required quality for quasars selected according to the user's definition. The most efficient implementation of the target selection process might involve the integration of the query procedure into the observation/proposal preparation tool for the particular instrument, thereby enabling the user to vary the proposed observational set-up and see how his/her list of candidate targets varied as a result.

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KeyReferences:

Jim Dunlop (IfA, Edinburgh), private communication

Kukula M.J., Dunlop J.S., McLure R.J., Miller L., Percival W.J., Baum S.A., O'Dea C.P., 2001, MNRAS, 326, 1533

McLure R.J., Dunlop J.S., 2001, MNRAS, 327, 199

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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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Similar to some otehr cases in terms of what it needs, but a good science driver.

-- NicholasWalton - 17 Apr 2002

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-- BobMann - 15 Feb 2002