Presentation on theme: "Characterization 2 and Provenance data models. Use cases and first roadmap F.Bonnarel (CDS)"— Presentation transcript:
Characterization 2 and Provenance data models. Use cases and first roadmap F.Bonnarel (CDS)
Observation Use cases Char in the last phase of recom process To be enriched and completed by provenance, IVOA dm wg must go on. Analysis use cases: –Spectroscopy astronomers ask for description of apertures (spectro and photometry) and of beams or PSF, for cross- calibrations and SED building
Common problem(s) Garcia Lario (ESAC spectroscopy workshop) characterisation model Use of large, uniformly calibrated data sets usually helps but it is not enough Full characterisation is not always possible Need of extra information not yet available through the VO in many cases Beam profile/aperture description, filter transmission profiles, photometric zero points, spectral resolution information are only examples of additional information needed to properly communicate existing VO applications (e.g. through PLASTIC) Quality information is a world apart because of its complexity Filter services and footprint services are a step forward Need of a common access protocol to handle this information (as part of the metadata?) Data providers must be conscious that this additional information is essential to handle their data properly in a VO environment Other information not so critical but also useful, e.g.: Object type (to facilitate queries), time info in catalogues (to generate light curves), links to publications, etc.
General information (A Boselli ESAC Spectroscopy Workshop) Filter response: this is crucial for transforming observed magnitudes (VEGA SYSTEM) in monochromatic fluxes, and for comparing fluxes with models (synthetic magnitudes) for all photometric systems Coordinates: to avoid confusion for unresolved sources or extended objects PSF: to avoid confusion for unresolved sources Aperture: fundamental for extended sources or crowded regions Applied corrections: extrapolation to total values; extinction corrections…
Concluding remarks (A Boselli ESAC Spectroscopy Workshop) Filter response: this is crucial for transforming observed magnitudes in monochromatic fluxes (necessary for the construction of SED), and for comparing fluxes with models (synthetic magnitudes) for all photometric systems Coordinates, PSF, Apertures….: to avoid confusion for unresolved sources or extended objects and in crowded regions Applied corrections: extrapolation to total values; extinction corrections…; we choose to present uncorrected data to leave to the astronomer the possibility of choosing is own method References: should be available for the definition of each variable, units,… (prefer only published data checked by a referee) Keep any possible information on the quality of the data
Observation use cases –Transmission curves and Photometric Zero points and calibration (see Jonathans talk) usefull for SED building, surface photometry, catalog photometric characterisation.(absolute comparisons) Links: –Complex datasets: CCD mosaics, IFU –HST association, CFHTLS/TERAPIX stacking –Convenient visualisation = views –Reprocessing: Calibration process raw data and calib data
Observation use cases WCS or pixel/absolute coord mapping (integrate what is available in WCS in the Observation model) Quality assesment by checking Observation actual history: –atmospheric conditions and instrumental config.
Observation models: what does exist? IVOA observation model (2004, IVOA Note) Astronomy Domain Model CADC Observation data model Radio Models (ALMA …) Photometry proposal by Jonathan (added to spectrum or used as a « CoordSys » on the flux axis). Mapping (D Berry and STC +WCS papers) Interop presentations in Victoria (AccessAndViews DM) and Beijing
RoadMap Implement Char 1 in services Build a Char2/provenance subgroup by email: discussing Use cases Organize a dedicated meeting before May interop (January ?) to design a solution Produce a draft (internal if note working) a little before May Interop.
Acknowledgments Mireille Louys and J McDowell for discussion in the last days Many other DM group members for previous discussions (Alberto, Anita, Igor, Daniel, Andreas, Pat, Gerard, Doug etc,etc,etc…)