SPECTRAL CLASSIFICATION AND REDSHIFT MEASUREMENT FOR THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY

By A. Bolton, David Schlegel, E. Aubourg, Stephen Bailey, V. Bhardwaj, J. Brownstein, S. Burles, Yan-Mei Chen, K. Dawson, Daniel J. Eisenstein and 22 more. 2012

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We describe the automated spectral classification, redshift determination, and parameter measurement pipeline in use for the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III (SDSS-III) as of the survey's ninth data release (DR9), encompassing 831,000 moderate-resolution optical spectra. We give a review of the algorithms employed, and describe the changes to the pipeline that have been implemented for BOSS relative to previous SDSS-I/II versions, including new sets of stellar, galaxy, and quasar redshift templates. For the color-selected “CMASS” sample of massive galaxies at redshift 0.4 ≲ z ≲ 0.8 targeted by BOSS for the purposes of large-scale cosmological measurements, the pipeline achieves an automated classification success rate of 98.7% and confirms 95.4% of unique CMASS targets as galaxies (with the balance being mostly M stars). Based on visual inspections of a subset of BOSS galaxies, we find that approximately 0.2% of confidently reported CMASS sample classifications and redshifts are incorrect, and about 0.4% of all CMASS spectra are objects unclassified by the current algorithm which are potentially recoverable. The BOSS pipeline confirms that ∼51.5% of the quasar targets have quasar spectra, with the balance mainly consisting of stars and low signal-to-noise spectra. Statistical (as opposed to systematic) redshift errors propagated from photon noise are typically a few tens of km s−1 for both galaxies and quasars, with a significant tail to a few hundreds of km s−1 for quasars. We test the accuracy of these statistical redshift error estimates using repeat observations, finding them underestimated by a factor of 1.19–1.34 for galaxies and by a factor of two for quasars. We assess the impact of sky-subtraction quality, signal-to-noise ratio, and other factors on galaxy redshift success. Finally, we document known issues with the BOSS DR9 spectroscopic data set and describe directions of ongoing development.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/d479d5562e4187a3905db9c01ebadc058d64d1cb

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Citations in the corpus

The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological analysis of the DR12 galaxy sample (2016, background): “Smee et al. (2013) provide a detailed description of the spectrographs, and Bolton et al. (2012) describe the spectroscopic data reduction pipeline and redshift determination.”
The SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations at Redshift of 0.72 with the DR14 Luminous Red Galaxy Sample (2017, methodology): “The final eBOSS LRG spectra were classified and their redshifts measured primarily by redmonster20 (Hutchinson et al. 2016), complemented by redshifts obtained using spec1d (Bolton et al. 2012).”
The Sloan Digital Sky Survey quasar catalog: ninth data release (2012, methodology): “The current spectroscopic reduction pipeline for BOSS spectra is described in Bolton et al. (2012).”
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological implications of the full shape of the clustering wedges in the data release 10 and 11 galaxy samples (2013, methodology): “The remaining redshifts were measured from the spectra obtained with the double-armed BOSS spectrographs (Smee et al. 2013) by applying the minimum-χ2 template-fitting procedure described in Aihara et al. (2011) and Bolton et al. (2012).”
Discovery of extreme [O III] λ5007 Å outflows in high-redshift red quasars (2015, background): “…redshifts zin (listed in Table 1) which are obtained by cross-correlating the optical (rest-frame ultraviolet) spectra against pre-defined templates (Bolton et al. 2012; in our case, against a normal blue type 1 quasar template), but with an understanding that they are not necessarily accurate.”
The clustering of galaxies in the SDSS-III DR9 Baryon Oscillation Spectroscopic Survey: constraints on primordial non-Gaussianity (2012, unknown): “Redshifts are determined as described in Bolton et al. (2012).”
Measurement of baryon acoustic oscillations in the Lyman-α forest fluctuations in BOSS data release 9 (2013, methodology): “Using the Lyman-α forest to measure the 3D structure of the Universe became possible with the advent of the Baryonic Oscillation Spectroscopic Survey (BOSS, [26, 27]), a part of the Sloan Digital Sky Survey III (SDSS-III) experiment [28–33].”
THE SDSS-IV EXTENDED BARYON OSCILLATION SPECTROSCOPIC SURVEY: OVERVIEW AND EARLY DATA (2015, methodology): “It consists of two main parts: the “spectro2d” portion that extracts two-dimensional raw data into one-dimensional flux calibrated spectra; and the “spectro1d” portion that measures scalar quantities such as classifications and redshifts from those one-dimensional spectra (Bolton et al. 2012).”
THE ELEVENTH AND TWELFTH DATA RELEASES OF THE SLOAN DIGITAL SKY SURVEY: FINAL DATA FROM SDSS-III (2015, methodology): “The classification and redshift-measurement aspects of this software are described in Bolton et al. (2012).”
The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release (2020, methodology): “Observed spectra are fit by a set of models and templates that are detailed in Bolton et al. (2012).”
The SAGA Survey. I. Satellite Galaxy Populations around Eight Milky Way Analogs (2017, methodology): “To check that our gri color cuts are not missing faint low redshift galaxies in a larger sample, we search the SDSS CMASS survey (Bolton et al. 2012).”
Clustering of intermediate redshift quasars using the final SDSS III-BOSS sample (2015, methodology): “To avoid using any target with a problematic redshift, we only accept quasars with zWARNING=0, indicating a confident spectroscopic classification and redshift measurement forquasar targets (Bolton et al. 2012)2.”
Intrinsic alignments of SDSS-III BOSS LOWZ sample galaxies (2014, methodology): “Targets are assigned to tiles of diameter 3◦ using an adaptive tiling algorithm (Blanton et al. 2003), and the data was processed by an automated spectral classification, redshift determination, and parameter measurement pipeline (Bolton et al. 2012).”
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: RSD measurement from the power spectrum and bispectrum of the DR12 BOSS galaxies (2016, unknown): “As part of the Sloan Digital Sky Survey III (Eisenstein et al. 2011) the Baryon Oscillation Spectroscopic Survey (BOSS) (Dawson et al. 2013) measured spectroscopic redshifts (Bolton et al. 2012; Smee et al. 2013) for more than 1 million galaxies and over 200 000 quasars.”
Extragalactic science, cosmology, and Galactic archaeology with the Subaru Prime Focus Spectrograph (2012, background): “3 (Gpc/h)3, a factor 2 larger volume than the SDSS BOSS galaxy survey, which is about4.”
The Completed SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations with Lyα Forests (2020, methodology): “This estimator is similar to the estimator of the standard pipeline (Bolton et al. 2012), but we do not use wavelengths in the vicinity of the Lyα emission line or at shorter wavelengths.”
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Cosmological implications of the configuration-space clustering wedges (2016, methodology): “After identifying the galaxies with previous spectroscopic observations from the SDSS I/II surveys (York et al. 2000), the remaining redshifts were measured from the spectra obtained with the BOSS spectrographs (Smee et al. 2013) as described in Aihara et al. (2011) and Bolton et al. (2012).”
Baryon acoustic oscillations in the Lyα forest of BOSS DR11 quasars (2014, methodology): “The data were reduced with the SDSS-III pipeline as described in Bolton et al. (2012).”