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| SDSS photometric system | |
|---|---|
| Name | SDSS photometric system |
| Created | 1998 |
| Survey | Sloan Digital Sky Survey |
| Bands | u g r i z |
| Wavelength range | 300–1100 nm |
| Telescope | Apache Point Observatory 2.5 m |
| Detector | CCD mosaic |
SDSS photometric system The SDSS photometric system is the five-band imaging system developed for the Sloan Digital Sky Survey, used to measure astronomical broadband magnitudes across the optical and near‑ultraviolet. It underpins catalogs produced by the Sloan Digital Sky Survey, enabling large-scale studies of galaxies, quasars, stars, and the large-scale structure of the Universe. The system is tightly coupled to the Sloan Digital Sky Survey instrumentation, survey strategy, and data reduction pipelines developed at institutions such as the Fermilab, Princeton University, and the Apache Point Observatory.
The SDSS photometric system was designed to provide uniform, wide‑field photometry for surveys like the Sloan Digital Sky Survey and follow‑on projects including SDSS-II, SEGUE, and BOSS. It employs a dedicated imager mounted on the Apache Point Observatory 2.5‑meter telescope and an array of charge‑coupled devices produced by groups associated with Fermilab and the University of Washington. The system is integral to catalogs distributed by the Sloan Digital Sky Survey Collaboration and used by researchers at institutions such as Princeton University, University of Chicago, and University of Washington.
The five filters, commonly labeled u, g, r, i, z, cover roughly 300–1100 nm and were chosen to sample features used in extragalactic and stellar classification, complementing instruments at facilities like the Hubble Space Telescope and the Palomar Observatory. The transmission profiles incorporate contributions from the imager optics, CCD quantum efficiency manufactured by vendors collaborating with Fermilab, and atmospheric extinction typical at the Apache Point Observatory. The passbands were characterized with reference standards established by observatories such as U.S. Naval Observatory and calibration work by teams at Princeton University and University of Washington.
Calibration anchored the system to a set of primary standards maintained by groups like the U.S. Naval Observatory and the International Astronomical Union federated networks used by European Southern Observatory teams. Absolute and relative zeropoint determination used extinction monitoring, nightly calibration fields, and overlapping scan strategies coordinated by the Sloan Digital Sky Survey Collaboration and processed at computing centers including Fermilab and Johns Hopkins University. Cross‑calibration with external catalogs from projects like the Two Micron All Sky Survey and the Galaxy Evolution Explorer aided color transformations and zeropoint checks employed by researchers at Princeton University and University of Chicago.
Imaging data passed through automated pipelines developed by teams at institutions such as Fermilab, Princeton University, and Johns Hopkins University to perform bias subtraction, flat‑fielding, astrometric solutions tied to the USNO-B Catalog, and object detection influenced by algorithms from the Hubble Space Telescope data reduction community. The photometric pipeline produced model, PSF, and Petrosian magnitudes used widely in analyses by collaborators at Princeton University, University of Chicago, and Space Telescope Science Institute. Data releases were managed by the Sloan Digital Sky Survey Collaboration and accessed through archives hosted by institutions including University of Chicago and Fermilab.
Photometric precision depended on factors monitored by observatory teams from Apache Point Observatory and calibration groups at Princeton University: atmospheric transmission variation, CCD nonlinearity, and scattered light. Systematic errors were quantified in data releases by the Sloan Digital Sky Survey Collaboration and studied by external groups at University of Chicago and Johns Hopkins University. Limitations include reduced sensitivity in the u band compared to bands used by the Hubble Space Telescope and color terms when transforming to legacy systems such as the Johnson–Cousins photometric system used in historical surveys coordinated by the International Astronomical Union.
The SDSS photometric system enabled major results in extragalactic astronomy and cosmology pursued by teams at Princeton University, University of Chicago, and Lawrence Berkeley National Laboratory, including galaxy luminosity functions, photometric redshift estimation, and identification of quasars later followed up by the Keck Observatory and Very Large Telescope. Stellar population studies used SDSS colors in conjunction with spectroscopic programs like SEGUE and BOSS run by the Sloan Digital Sky Survey Collaboration and follow‑up teams at Apache Point Observatory and University of Washington. Large‑scale structure measurements derived from SDSS photometry contributed to analyses by groups at Lawrence Berkeley National Laboratory and Princeton University addressing clustering and baryon acoustic oscillations.
The system was developed in the mid‑1990s by the collaboration anchored at Princeton University, Fermilab, and Apache Point Observatory, with instrumentation efforts supported by institutions including University of Washington and Johns Hopkins University. Early technical descriptions and calibration strategies were published by teams involving the Sloan Digital Sky Survey Collaboration prior to the first public data release, which catalyzed wide adoption by research groups at Princeton University, University of Chicago, Lawrence Berkeley National Laboratory, and Space Telescope Science Institute.
Category:Photometric systems