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Spectrum Services 2007

Spectrum Services 2007. László Dobos (ELTE) dobos@complex.elte.hu Tamás Budavári (JHU), István Csabai (ELTE). MOTIVATIONS. SDSS Data Archive Server offers very limited possibility to search among spectra SkyServer has nice search features, but does not contain the spectra

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Spectrum Services 2007

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  1. Spectrum Services 2007 László Dobos (ELTE) dobos@complex.elte.hu Tamás Budavári (JHU), István Csabai (ELTE) VO Spectroscopy Workshop, ESAC 2007

  2. MOTIVATIONS • SDSS Data Archive Server offers very limited possibility to search among spectra • SkyServer has nice search features, but does not contain the spectra • Observed spectra are in many formats: • binning • wavelength scale (air / vacuum) • extinction correction • file format VO Spectroscopy Workshop, ESAC 2007

  3. SPECTRUM & FILTER SERVICES • Database of spectra • Wide range of search possibilities • Preprocessing spectra on the fly • Data analysis • Access to data in many file formats • Plot spectra • Web interface • Web service to program against • Filter service:database of optical instrument band-pass curves VO Spectroscopy Workshop, ESAC 2007

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  6. AVAILABLE SPECTRA • Repository of observed and theoretical spectra • SDSS DR1-DR5 (1M spectra in DR5 only) • 2dF (250k) • BaSeL stellar library • Bruzual-Charlot stochastic burst model library (100k) • 'My Spectrum' is a public repository where users can upload their own measurements or save results of spectrum processing. VO Spectroscopy Workshop, ESAC 2007

  7. SEARCH POSSIBILITIES • Cone search - search by coordinates and radius • ID search - if you know the database identifier (ie. from SkyServer) • Object search - by a list of coordinates • Redshift search • Advanced search - with many basic options • Region search - gives back spectra of objects in a complex, arbitrary area • Similarity search - based on PCA VO Spectroscopy Workshop, ESAC 2007

  8. 3. REGION SEARCH • The new Footprint Service allows defining complex regions on the sphere • Spectrum Services link to the Footprint Service to get region description • Spectra observed in the given region can be retrieved from the database VO Spectroscopy Workshop, ESAC 2007

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  10. 4. SIMILAR SPECTRUM SEARCH • Spectra are expanded on a predefined basisPCA (see Ching-Wa's talk) or model spectra • Coefficients are stored in a multi-dimensional database • Database is indexed by special spatial indices • N-Nearest neighbour search in the coefficient space • Not necessarily physical, still interesting VO Spectroscopy Workshop, ESAC 2007

  11. GALAXIES VO Spectroscopy Workshop, ESAC 2007

  12. PREPROCESSING TOOLS • General functions to convert spectra to the same format to use in analysis • Functions: • Correction for galactic extinction • Rest frame • Normalization • Rebinning • Vacuum - Air wavelength conversion • Download preprocessed spectra (XML, VOTable, ASCII) • Store them in 'MySpectrum' for later use VO Spectroscopy Workshop, ESAC 2007

  13. ANALYSIS TOOLS • Composite spectrum: • average, median • Convolution with filters from Filter Servicesynthetic magnitude calculation • Continuum and line fitting • The new version will be really fast: • Parallel computation on multiple processor • optimized LAPACK libraries VO Spectroscopy Workshop, ESAC 2007

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  15. SUMMARY & FUTURE WORKS • Spectrum database and public repository • Web site & web service • Integration with other VO services: • Filter Service, Footprint Service • Preprocessing and analyzis tools • Improved line fitting algorithm • Make similarity search public • Latest VO standard implementation VO Spectroscopy Workshop, ESAC 2007

  16. URLs OF INTEREST • Spectrum Services http://voservices.net/spectrum • Filter Service http://voservices.net/filter • Footprint Service http://voservices.net/footprint VO Spectroscopy Workshop, ESAC 2007

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  18. Distribution of SDSS objects in the space of SDSS galaxy eigenspectra Galaxies Stars QSOs VO Spectroscopy Workshop, ESAC 2007

  19. WEB INTERFACE • For interactive use by humans • Concept: try the functions on the web page, but use the web service for batch processing • Register / login • Search and display results in a nice format • 'Wizards' to guide users through the pages of many parameters of scientific functions • Download spectra in XML, VOTable, ASCII • (No implementation of the latest DM yet) VO Spectroscopy Workshop, ESAC 2007

  20. 2. SPEEDING UP SPECTRUM SERVICES • Objective: processing hundreds of thousands of spectra • Moved to .Net 2.0- Better computing performance • Streamlined processing of spectra • Minimal memory usage • No upper limit for number of spectra • Multi-processor support • parallel execution of processing routines • Optimized LAPACK integration: • MKL (intel), ACML (AMD) VO Spectroscopy Workshop, ESAC 2007

  21. 4.1 THE ECOEFF SPACE • DR4 galaxy eigenspectra used as basis(Yip et. al 2002) from gappy PCA algorithm • All spectra (even stars and QSOs) are expressed on this basis • Our method: minimal χ2 fitting (with masks etc.) • Applied to: • SDSS DR5 • Charlot's stochastic 100k spectrum set • Objective: find physical parameters very quickly VO Spectroscopy Workshop, ESAC 2007

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