EÖTVÖS UNIVERSITY BUDAPEST Department of Physics of Complex Systems VO Spectroscopy Workshop, ESAC Spectrum Services 2007 László Dobos (ELTE) Tamás Budavári (JHU), István Csabai (ELTE)

VO Spectroscopy Workshop, ESAC 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 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

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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 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 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

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10 4. SIMILAR SPECTRUM SEARCH Spectra are expanded on a predefined basis PCA (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 GALAXIES

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

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VO Spectroscopy Workshop, ESAC 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 URLs OF INTEREST Spectrum Services Filter Service Footprint Service

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

VO Spectroscopy Workshop, ESAC 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 SPEEDING UP SPECTRUM SERVICES Objective: processing hundreds of thousands of spectra Moved to.Net 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 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 χ 2 fitting (with masks etc.) Applied to: –SDSS DR5 –Charlot's stochastic 100k spectrum set Objective: find physical parameters very quickly