What can be done to make the Virtual Observatory useful for stellar population analysis?

1. What can be done to make the Virtual Observatory useful for stellar population analysis? Miguel Cerviño (SVO)1,2 Santi Cassisi (Vosb.It)1,2 Herve Wozniak (VO-France)1,2 1Theory Expert Group (EuroVO-DCA) 2Theory Interest Group (IVOA) IAU Symp. 241 Dec. 2006

2. IAU Symp. 241 Dec. 2006 What is VO? The Virtual Observatory will be a system that allows astronomers to interrogate multiple data centers in a seamless and transparent way, which provides new powerful analysis and visualization tools within that system, and which gives data centers a standard framework for publishing and delivering services using their data. This is made possible by standardizationof data and metadata, by standardization of data exchange methods, and by the use of a registry, which lists available services and what can be done with them. Where is the “system”? Does it mean operative system? NO, it means aworking environment, just like KDE, Gnome or Windows … but it says “their data”… Does it mean using “analysis tools” with data from different machines and formats whatever the operating system? YES!! Uhmm, does it mean something like IRAF? But there is a lot of software already…. Ok, so it is needed a standard way to DESCRIBE data (besides the “data format” that does not need to change) so the MAIN POINT is HOW TO DESCRIBE the data themselves (metadata)… … and to establish the communication between machines… … and “yellow-pages” for search resources… The long term vision is not one of a fixed specific software package, but rather one of a framework which enables data centers to provide competing and co-operating data services, and which enables software providers to offer a variety of compatible analysis and visualization tools and user interfaces. The first priority for the VO projects worldwide is to develop the standardized framework, which will allow such creative diversity. International Virtual Observatory Alliance Guidelines for Participation http://ivoa.net/Documents/latest/IVOAParticipation.html

3. IAU Symp. 241 Dec. 2006 What can VO do for stellar population analysis? • For model developers: Common way to describe/tranfer/use the data • VOtable: Data description + data (any format) • It is not needed different “drivers” for different inputs and/or different groups (atmosphere libraries, tracks, isochrones, SSPs...) • For model users: Democracy in model use (democracy = to make a choice and to be able to justify this choice in a physical bases) • Common way to use data • All model with similar visibility • You can chose the best model (or model subset) • It will need that model developers explain differences among models (but it is also needed otuside VO world ;) • Remember SSP challenge results: use different models (including different algorimths: Fuel Consumption vs. Isochrone synthesis) to test your result

4. IAU Symp. 241 Dec. 2006 Inside VO No-VO You can choose! And you can justify Your choice based in physical reason!

5. IAU Symp. 241 Dec. 2006 What can be done to make the VO useful for stellar population analysis? • VO can is yet useful for stellar populations!! • It can retrieves observational data • It can retrieves theoretical data (SSPs etc...) • But it can be much more useful: • If model developers are able to describe explicitly the assumptions that are done implicitly (and sometimes not described in papers): e.g. Are atmospheres interpolated? How are isochrones obtained? Which and how interpolations are used? Which method is use to integrate the isochrone? How deals with isochorne points outside the parameter space covered by the atmosphere library? Any case, it is not a VO requisite, but a science requisite

6. IAU Symp. 241 Dec. 2006 • 2.- If we establish what a model result is: • - A deterministic result? (given age/ metalicity/ SFH/ IMF/ extinction...) a unique value of the integrated luminosity? - A probabilistic result? - Generally provides a mean value of a distribution - But also provide (sometimes) the variance of such distribution, parameterized as Surface Brightness Fluctuations - And why do not use skweenes and kurtosis also? • - And why not all the distribution? (e.g. Monte Carlo simulations) Note: It also affects to tracks/isochrones (e.g. rotation, TP-AGB...), results of SSP challenger results (best 2 vs. 2 distribution) etc... Again, it is not a VO requisite, but a science requisite, since it affects its use and interpretation

7. IAU Symp. 241 Dec. 2006 Conclusions • VO idea is to help to produce science more efficiently • VO its in a no-return point (models are there and will be there; either provide by developers or provide by third-parties) • VO is now useful for stellar population analysis, but it can be much more useful • At this moment, VO requirements are also science requirements • If you are interesting, we will create a mailing list to define what and how describe atmosphere/ tracks/ isochrones/ synthesis models/ analysis tools etc.. (contanct Herve, Santi, or Miguel)