Astronomy databases

Astronomy databases include both homogeneous and inhomogeneous ones (i.e. collected from a variety of sources). Recall there is no such thing as perfect data, so one should always consider how the data were obtained and potential limitations. This may become more of an issue as we evolve towards larger and larger projects for which automated processing becomes essential.

Example: pipeline data quality: bogus SDSS quasars in the EDR

Example: selection effects: high-redshift rotation curves

General data bases

• ADS (http://adswww.harvard.edu): Publications
• ADC (http://adc.gsfc.nasa.gov): various catalogs
• CADC (http://cadcwww.dao.nrc.ca): nice front-end to lots of catalogs
• NED (http://nedwww.ipac.caltech.edu): extragalactic object front-end
• SIMBAD/CDS (http://cdsweb.u-strasbg.fr/Simbad.html: many published tables/catalogs

Specific project databases

• HST (http://archive.stsci.edu)
• 2MASS (http://www.ipac.caltech.edu/2mass/)
• SDSS (http://ganymede.nmsu.edu/sdss/)

SDSS

Survey overview: image roughly 1/4 celestial sphere using drift scanning in 5 colors (ugriz). Follow-up spectroscopy of roughly 1 million galaxies. Drift scanning produces stripes across sky, obtained in two strips; there is some overlap. Imaging camera has 6x5 CCDs, each 2Kx2K.

Data reduction by pipeline. Objects identified by run, rerun, camcol, field, object. A run is a single drift-scan across the sky.

Data products:

• SDSS database: includes position, flux, shape information on all objects, redshift, classification, and line strengths of those with spectra. Note data flags.
• Spectra
• Atlas images
• Corrected images

Data interfaces:

• Sky server
• MAST
• sdssQT
• FNAL image retrieval