ScienceProblem: GalaxyMorphologyProbingStarFormation

PrimaryActor:

astronomer

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ScienceGoal:

compare morphological data of galaxies at different rest frame wavelengths and at differing redshifts to assess various models of galaxy formation mechanisms.

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DataSets:

for high redshift galaxies, deep high spatial resolution data sets are required. This often points towards satellite datasets from e.g. HST. Chandra data in the X-ray will also now be useful.

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ProblemDescription:

Classically galactic bulges were thought to form at hi-z through dissipationless collapse (Eggen et al 1962). The more recent Hierarchical models (e.g. Baugh et al 1998) propose that elliptical galaxies form via mergers of early disk systems, these in turn continue to arccrete gas and thus form spiral's.

If the Hierarchical models are correct, then the stars in the bulges of spiral galaxies must be older (redder) than those in ellipticals at the same z (Ellis et al 2001).

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CurrentSolution:

HST images taken of galaxies in the optical and near-IR - those used to date being from the HDF-N and HDF-S fields. Usable data is available upto z~1.0 - greater than this the bulges are not resolvable.

'Simple' technique to determine bulge colors described by Ellis et al (2001) - galaxy size determined from fit to morphology, and bulge taken as 5% radius centred on the galaxy centroid. Optical colours then compared.

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VOSolution:

Exapand survey to search for more data sets - so those with correct spatial resolution and depth. Current work based on I and V band data (WFPC2) and J, H (NICMOS) data sets.

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Discussion:

Comparison of Optical and IR datasets involves smoothing of the Optical data to that of the IR data before the colours are computed.

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KeyReferences:

Baugh et al, 1998, ApJ, 498, 504

Eggen et al, 1962, ApJ, 136, 748

Ellis et al, 2001, ApJ, 551, 111

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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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Topical problem that will probably be addressed by the VO

-- NicholasWalton - 17 Apr 2002

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-- NicholasWalton - 16 Apr 2002