Re: IVOA theory sessions in Kyoto

>Dear colleagues

<>>
>I would like to know about the plans of any of you to go to the next
IVOA meeting in Kyoto and your interest in partaking in one or more sessions of
>the theory interest group. In particular I would like to know whether
you have anything you might like to contribute there, be it a demo or a
>presentation.
>Also, do you have any ideas about specific subjects that you would
like to see
>discussed?

Hello Gerard and dear colleagues,

Thank you for this proposition of TVO-IG session in Kyoto, I agree with the goals you are defining and I will normally attend.

I would like to add comments about a specific field of simulated data: SED or more generally spectra. In the recent AVO/EURO-VO science demo (in January in Madrid), two science-cases presented 'fits' of observed SEDs of galaxies against theroretical SEDs (in this case, models of stellar populations). The need for (i) having such theoretical data available and (ii) to fit them to observations was clearly expressed as a priority in the scientific discussions.

These applications are a first interesting example of introducing Theory. It is indeed easier to directly fit, or compare, observed and modelled spectra than comparing images (comparing spectra can be almost as simple as subtracting them).

Though during this demo it was possible to overplot models to observations, a number of important issues were left open, for example:

1. The current observational DM (Observation or SED) make mandatory informations like the position on the sky (or exposure time...), which are not relevant to modelled data. For this reason it is not possible to express a synthetic spectrum using the SED DM (so the demo was not based on 'pure-standards').
2. To compare models with observations, we have to take into account the transfert between the source and the observer (which is usually not considered as part of the model): So we need, for example, to tell if a spectrum is corrected for Galactic extinction, internal extinction (within the source)...

It seems that the current SED-DM could almost be used for a large range of modelled spectra (except the problems of point my (1)). And the question (2) could concern as well observation or model (we may like either to correct the observation, or to apply some effect to the model). However, other components of the DM are specific of the model: as described in the Provenance object of the excellent paper by L. Shaw and collaborators (on the TVO site).

I do not know how we should proceed, either include the theory specification in the more general Observation DM, make a T-DM covering everything from N-body simulations to spectrosopy or make distinct DM for each scientific case...

But I can work on the requirements for various applications of model of spectra, trying to connect them with the propositions of L. Shaw. And we could discuss it in Kyoto.

Philippe Prugniel. Received on 2005-03-25Z14:56:07