This project builds on the legacy of the two previous Sloan Digital Sky Survey programs (SDSS and SDSS-II). This project consists of four surveys.
The NSF funding is primarily for the Baryon Oscillation Spectroscopic Survey (BOSS). This survey will measure redshifts of 1.5 million luminous red galaxies and Lyman-alpha absorption towards 160,000 high redshift quasars. These measurements will permit the absolute cosmic distance scale to be determined to a higher precision (1.0-1.5%) than previously achieved and will provide constraints on the equation of state of dark energy. Some of the NSF funds will also be used to support the Apache Point Observatory Galactic Evolution Experiment (APOGEE). This survey will use high-resolution and high signal-to-noise infrared spectroscopy to penetrate the dust that obscures the inner Galaxy from our view, measuring radial velocities, spectral types, and detailed elemental abundances of 100,000 red giant stars to an H magnitude limit of approximately 13.5 across the full range of the Galactic bulge, bar, and disk.
The first of the non-NSF funded surveys is SEGUE-2 which will measure radial velocities, spectral types, and elemental abundances of 350,000 stars in numerous target categories to a g magnitude limit of approximately 19, which will probe the kinematics and chemical evolution of the outer Milky Way. The final survey, also non-NSF funded, is the Multi-Object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). This will monitor the radial velocities of 11,000 bright stars, with the precision and cadence needed to detect gas giant planets with orbital periods ranging from several hours to two years. These observations will provide a critical statistical data set for testing theories of the formation and dynamical evolution of planetary systems.
These surveys will produce large, well calibrated, easily accessible public databases supporting astronomical research and educational activities at many levels. The project also includes an active program of education and outreach promoting the data and tools to K-12 and university educators and to the broader public.
Sloan Digital Sky Survey III (SDSS-III) is nearing a very successful completion. As of October 2014, all observing has been completed, with BOSS and APOGEE both exceeding their data volume goals. Three public data releases have already been completed, including all SDSS-III imaging, 65% of BOSS spectroscopy, and 35% of APOGEE spectroscopy, as well as all SEGUE-2 and past SDSS-I and II data. Our final data release, including all of the data, is scheduled for the January 2015 AAS meeting. SDSS-III completed all of its development goals for BOSS and APOGEE. These included the design and construction of the new APOGEE instrument, the BOSS spectrograph upgrade, and numerous fiber system upgrades. The BOSS spectrograph has superb performance and is by reasonable measures the world's leading wide-field optical spectrograph. The APOGEE instrument is the first of its kind, a 300-fiber high-resolution infrared spectrograph featuring three JWST-class HR2G arrays and the first mosaiced volume-phase holographic grating to be fielded in an astronomical instrument. An extensive fiber system, including 8 facility cartridges that could be swapped quickly using fiber connectors, was built to exacting performance specifications. The instrument was completed in only two years from the preliminary design review to commissioning in summer 2011, meeting all requirements and functioning exceptionally well. The BOSS and APOGEE teams built high-performance data reduction pipelines to process the data. The BOSS reductions extend the SDSS data pipelines, while the APOGEE pipeline is new and includes an ambitious automated extraction of stellar parameters, with estimation of 15 separate elemental abundances. The Data team has included these data sets into feature-rich public on-line databases, with numerous access methods. A large amount of documentation and numerous refereed technical papers have already been produced, with more coming for the final data release. In total, the BOSS aquired spectroscopy of 2.2 million targets, covering just over our survey goal of 10,000 square degrees and producing the world's premier large-scale structure sample. BOSS also used the SDSS imaging camera to produce a contiguous image of 3200 square degrees in the South Galactic Cap. The BOSS data set has supported a wide range of science analyses, including the namesake project to measure the cosmic distance scale by the baryon acoustic oscillations (BAO). The results to date, based on 85% of the final data set, feature a 1.0% measurement of the distance to redshift 0.57 and 2.1% to redshift 0.32 from the galaxy sample. The 3-dimensional view of the intergalactic medium revealed from the Lyman-alpha forest in BOSS quasar sepctra yields a 5-sigma detection of BAO at redshift 2.3 and a 3% measurement of the Hubble parameter at this much earlier epoch. The BOSS BAO results play a central role in current cosmological constraints and provide a direct physical connection between the low-redshift Universe and that seen at redshift 1000 in the cosmic microwave background. The BOSS data have used for numerous other cosmology results, as well as astrophysical studies of galaxy evolution, quasars, and the intergalactic medium. APOGEE similar exceeded its data collection goals, acquiring survey quality spectra of 131,000 stars plus 15,000 hotter stars used for telluric standards. With S/N typically exceeding 100 per pixel at spectral resolution of 22,500, APOGEE is the world's leading collection of high-resolution, high-fidelity spectra at any wavelength. Owing to its infrared bandpass and exploiting the high IR luminosity of red giant stars, APOGEE has probed all components of the galaxy, most notably the bulge and beyond. APOGEE establishes a common abundance scale throughout the Galaxy and permits detailed investigation of subtle element-by-element abundance patterns. Numerous APOGEE science papers have already appeared, investigating Galactic structure, stellar populations, and even interstellar absorption. Several published studies have begun to tackle the central goal to understand the variations in stellar abundances across the Galaxy. Nevertheless, the bulk of the opportunity is still ahead, as the APOGEE team has been largely focused on the development and testing of the software pipelines to meet the deadline of the data release. In total, SDSS-III raised $45.76M of funding, with $9M from the NSF. We expect SDSS-III to complete its project activities in Q1 2015 on-cost and on-schedule. The SDSS-III Collaboration is a vibrant and world-wide activity, including 51 MOU institutions and over 900 scientists. So far, 145 papers have written by the collaboration, with a few dozen others written with the public data. Many others are under development. We are confident that the final data release will be a well-used legacy product. The success of SDSS-III has directly fostered the development of SDSS-IV, which has attracted a similarly large collaboration in continued pursuit of the SDSS, BOSS, and APOGEE science programs. SDSS-IV took over mountain operations in July 2014 and plans for a six-year program.
