The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey

TL;DR

SDSS-III DR9 presents the first spectroscopic data release from the BOSS survey, enabling BAO and Lyα forest science with a large galaxy and quasar sample. The release includes data from the first 1.5 years of BOSS, plus DR8/SEGUE-2, totaling roughly 536k galaxy spectra, 102k quasar spectra, and 91k stellar spectra, collected with upgraded instrumentation that extends wavelength coverage and improves throughput. It also reports astrometry corrections, updates to the SEGUE Stellar Parameter Pipeline, and new galaxy-derived quantities, along with robust data-distribution tools for public access. The paper frames DR9 as a foundation for cosmology, Galactic structure studies, and quasar science, and outlines DR10–DR12, which will incorporate APOGEE data and further BOSS observations.

Abstract

The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median z=0.52), 102,100 new quasar spectra (median z=2.32), and 90,897 new stellar spectra, along with the data presented in previous data releases. These spectra were obtained with the new BOSS spectrograph and were taken between 2009 December and 2011 July. In addition, the stellar parameters pipeline, which determines radial velocities, surface temperatures, surface gravities, and metallicities of stars, has been updated and refined with improvements in temperature estimates for stars with T_eff<5000 K and in metallicity estimates for stars with [Fe/H]>-0.5. DR9 includes new stellar parameters for all stars presented in DR8, including stars from SDSS-I and II, as well as those observed as part of the SDSS-III Sloan Extension for Galactic Understanding and Exploration-2 (SEGUE-2). The astrometry error introduced in the DR8 imaging catalogs has been corrected in the DR9 data products. The next data release for SDSS-III will be in Summer 2013, which will present the first data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) along with another year of data from BOSS, followed by the final SDSS-III data release in December 2014.

Figures (9)

• Figure 1: The distribution on the sky of all SDSS imaging (top; same as DR8) and BOSS DR9 spectroscopy (bottom) in equatorial coordinates ($\alpha=0^\circ$ is offset to the right in this projection). The Galactic equatorial plane is shown by the solid line. To make the image for BOSS spectroscopy, we simply plotted a sparse version of the BOSS quasar catalog paris12.
• Figure 2: The distribution with lookback time of the 82,645 stars; 493,845 galaxies; and 93,003 quasars with spectra in DR9 BOSS. Lookback time is based on the observed redshift under the assumption of a flat $\Lambda$CDM cosmology ($\Omega_M$,$\Omega_\Lambda$,$h$)=(0.272,0.728,0.71) consistent with the joint cosmological analysis of WMAP7 komatsu11.
• Figure 3: $N(z)$ of BOSS spectra in DR9 compared to that of the SDSS-I/II Legacy spectra for galaxies (left) and quasars (right). BOSS' focus on galaxies with $0.4<z<0.6$ and quasars with $z > 2.15$ is apparent. The BOSS quasars at $0.5<z<0.9$ are selected because of a degeneracy in color space between these lower-redshift quasars and those at $z>2.15$.
• Figure 4: S/N per pixel distribution of DR9 BOSS plates (red), compared with the equivalent for DR7 SDSS-I/II plates (black). The quantity shown is the square of the S/N, measured at a fiducial fiber magnitude. In SDSS-I and SDSS-II, these fiducial magnitudes differ somewhat (and the flux is measured through a $3$ fiber, not a $2$ fiber); these effects have been accounted for in this figure to make a fair comparison.
• Figure 5: A galaxy (upper panels) and a quasar (lower panels) that were observed in both SDSS-I/II (as released in DR7) and BOSS. These spectra are unsmoothed. In addition to the extended BOSS wavelength coverage from 3600 to 10,400 Å, the estimated noise per pixel (red line) is lower at every wavelength for the BOSS spectra, particularly at the red and blue ends of the spectrum. This is consistent with the higher S/N of the BOSS spectra shown in the distributions in Fig. \ref{['fig:boss_snr']}. Because the SDSS-I/II spectra are observed through $3"$ fibers, while the BOSS spectra use $2"$ fibers, one does not expect the galaxy spectra to be identical.