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Analysing data in the Virtual Observatory: Spectra of stellar populations

Analysing data in the Virtual Observatory: Spectra of stellar populations. Philippe Prugniel Observatoire de Lyon & Observatoire de Paris. Context. The VO is presented as a mean to facilitate astronomical research By discovering and accessing data (observations and models)

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Analysing data in the Virtual Observatory: Spectra of stellar populations

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  1. Analysing data in the Virtual Observatory:Spectra of stellar populations Philippe Prugniel Observatoire de Lyon & Observatoire de Paris Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  2. Context • The VO is presented as a mean to facilitate astronomical research • By discovering and accessing data (observations and models) • By extracting the information (statistics, fits to models …) Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  3. Context • The VO is presented as a mean to facilitate astronomical research • By discovering and accessing data (observations and models) • By extracting the information (statistics, fits to models …) • Responsibility of VO is to provide the standards and some infrastructure (like libraries to use the standards, validators…) • Standards for data exchanges, query protocols… • Description of the data Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  4. Context • The VO is presented as a mean to facilitate astronomical research • By discovering and accessing data (observations and models) • By extracting the information (statistics, fits to models …) • Responsibility of VO is to provide the standards and some infrastructure (like libraries to use the standards, validators…) • Standards for data exchanges, query protocols… • Description of the data • It is a big task • Because the standards need to be general • Need consensus in an heterogeneous community • … need compromises Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  5. Guided by science cases • Classify / identify stellar spectra • … • Analyse spectra of stellar populations Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  6. Observed spectrum Star Formation History … Fit Modelled spectrum Fitting population spectra As good as possible Get as much as possible from the observations Better than the observations Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  7. Observed spectrum Star Formation History … Fit Modelled spectrum Fitting population spectra As good as possible Get as much as possible from the observations Better than the observations Approaches: Spectrophotometric indices -> well calibrated, but uses only a fraction of the signal SED fitting (Shape of the spectrum) -> sensitive to extinction & flux calibration uncertainties Spectrum fitting (Absorption lines) -> importance of the spectral resolution Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  8. Observed spectrum Star Formation History … Fit Modelled spectrum Fitting population spectra As good as possible Get as much as possible from the observations Better than the observations Approaches: Spectrum fitting: Absorption lines -> importance of the spectral resolution Fits simultaneously the characteristics of the stellar population and the internal kinematics Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  9. Observed spectrum Star Formation History … Fit Modelled spectrum Fitting population spectra As good as possible Chilingarian 2006, thesis Get as much as possible from the observations Better than the observations Approaches: Spectrum fitting: Absorption lines -> importance of the spectral resolution Fits simultaneously the characteristics of the stellar population and the internal kinematics Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  10. Why do we want the VO there? • More modularity in the spectral modelling to understand the discrepancies between the codes? • Give a simple access to a complex method Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  11. Discrepancies between the models SSPs Bruzual & Charlot ‘03 Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  12. Discrepancies between the models SSPs Inversion by Pegase.HR Le Borgne + ,04 Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  13. Discrepancies between the models Is it due to the stellar libraries? To the way they are interpolated? To implementation aspects in the programs? To the physics of the model? Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  14. Is it due to the stellar libraries? To the way they are interpolated? To implementation aspects in the programs? To the physics of the model? Easy… Just have to permute the libraries or the physical ingredients … Discrepancies between the models Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  15. Is it due to the stellar libraries? To the way they are interpolated? To implementation aspects in the programs? To the physics of the model? Easy… Just have to permute the libraries or the physical ingredients … Aie…* The synthesis programs have proprietary formats for the libraries and for the physical ingredients, they are not fully documented nor publicly available… Discrepancies between the models * Ouch Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  16. Discrepancies between the models Is it due to the stellar libraries? To the way they are interpolated? To implementation aspects in the programs? To the physics of the model? Easy… Just have to permute the libraries or the physical ingredients … Aie… The synthesis programs have proprietary formats for the libraries, for the physical ingredients, they are not fully documented not publicly available… Koleva et al. 2007 Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  17. Discrepancies between the models To understand the differences between analyses performed with various methods and models, ones needs to check individually each ingredient, or each module. We are seeking for interoperable bricks… We need a VO workflow. Is it due to the stellar libraries? To the way they are interpolated? To implementation aspects in the programs? To the physics of the model? Easy… Just have to permute the libraries or the physical ingredients … Aie… The synthesis programs have proprietary formats for the libraries, for the physical ingredients, they are not fully documented not publicly available… Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  18. Stellar libraries isochrones 3D obs & cal Stellar libraries interpolation Data reduction PEGASE.HR Resolution matching Galactic extinction Adaptive filter (tessellation) Inversion 1D-extraction Field reconstruction Simple access to a complex process Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  19. Simple access to a complex process Stellar libraries Stellar libraries interpolation Elodie interpolator, SSA in the VO (see poster session) Other benefice of VO services: A function can have different usages than the one for which it was developed… Here: do stellar classification Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  20. Server: model Server: model fitting engine Client: GUI fitting engine visu Client: GUI visu How to fit? or Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  21. Server: model fitting engine Client: GUI visu How to fit? Server: model or Client: GUI fitting engine visu Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

  22. Spectra of stellar populations: summary • Use the VO as a framework for the comparisons of the ingredients of complex models • Extract individual functions of a wider interest, useful in different contexts • Develop workflows in the VO Spectroscopy and the VO -- Philippe Prugniel -- ESAC 21-23 March 2007

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