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Session 13 - Surveys, SETI and Pollution.
Display session, Monday, June 08
Atlas Ballroom,
The Sloan Digital Sky Survey will shortly begin imaging 10,000 square degrees of the northern high-latitude sky to approximately magnitude 22 in five special filter bands from roughly 3500 to 9000 Å\hspace 1 mm (Fukugita et al. 1996, Astron. J. 111, 1748). The resulting photometry of roughly 100 million objects (stars, galaxies, quasars, etc.) will be used to select targets for multifiber spectroscopy, as well as constitute a permanent archive for a large variety of astrophysical problems. For both of these functions, it is imperative to understand whether (and how) interesting subclasses of objects stand out of the normal stellar locus in multi-color space. Further, the precise transformation between the SDSS color system and more traditional ones will become very important for a variety of future studies.
Although the exact SDSS photometric system requires use of the actual survey telescopes, cameras, and filters, it is already possible to mimic the system reasonably well. Here we report observations carried out at the USNO 1-m telescope with an SDSS filter set. Using a locus of more than 1700 field stars in multi-color space, we show that cataclysmic variables separate from the stellar locus (best in u - g^* vs. g^* - r^*), while carbon stars separate from the stellar locus best in r^* - i^* vs. g^* - r^*, more so at the reddest colors. Most asteroids lie along the stellar locus and are not distinguishable from stars on the basis of their colors. Many asteroids of course will be identifiable owing to their motions. However, R-type asteroids do separate from the stellar locus in Sloan color space (in i^* - z^* vs. r^* - i^*). Because C-type asteroids are about 0.25 mag bluer in g^* - r^* than other types of asteroids, they can easily be differentiated from other types of asteroids on the basis of their Sloan colors. Work similar to this has been carried out on quasars, galaxies, and field stars by Richards et al. (1997, PASP 109, 39) and by Newberg et al. (1997, BAAS 29, 1385).
