Introduction

We discuss in this section some highlights of the scientific returns we expect from a comparison of the results of the SDSS with those of various NASA missions. NASA has led the way in the provision to the astronomical community of large, well calibrated, easily used data bases and catalogues from NASA missions (e.g. the COBE, IRAS and HST archives) and from the literature (e.g. the NASA/IPAC Extragalactic Data Base). Some of the most fruitful areas of research in recent years have depended on the multiwavelength studies enabled by these data bases, such as the selection from the IRAS data bases of catalogues for optical redshift surveys, the analysis of the dynamics of rich clusters of galaxies from X-ray fluxes and optical redshifts, and countless other examples.

The data products which the Sloan Digital Sky Survey is expected to provide include:

  1. Catalogues of objects to about r' = 23m covering the sky above about galactic latitude 30° (the "Northern" survey). There will be many x 107 stars and galaxies with accurate flux densities and positions in five colors observed at a resolution of about 1" with radial profile measures, shape parameters and a rough shape classification. In addition, the data base will contain CCD pictures (`atlas images') in five colors of every detected object.
  2. A full resolution photometric map of the sky in five colors
  3. A map binned in 4 x 4 pixels
  4. Spectra and redshifts of 106 uniformly selected galaxies, 105 quasars and large numbers of other objects
  5. An easily accessible data archive
  6. Photometry about 2m deeper in a strip along the celestial equator in the South Galactic Cap (the "Southern Survey")
  7. Repeat observations of large numbers of objects
  8. The ability to extract atlas images at the positions of objects detected at other wavelengths
  9. Spectra of additional objects in fields containing fewer than 640 primary spectroscopic targets (galaxies and quasars) (cf. Chapter 12)
A major effort is underway to build the SDSS archives for use both for running the survey and for science activities by the SDSS scientists, and these archives will develop to become the public distribution system (see Appendix C).

The combination of the SDSS data with those from the NASA data bases will yield vast amounts of science; we discuss a small subset below. We emphasize that there are no formal agreements with any of these NASA projects with the exception of ROSAT, and that discussing them here in no sense amounts to an `endorsement' of the SDSS by these projects or an agreement by them to cooperate with us. Rather, informal conversations and exchange of information have been going on, with all parties fully recognizing the potential payoffs of this work.