TY - JOUR
T1 - Spectral classification and redshift measurement for the SDSS-II Bayron Oscillation Spectroscopic Survey
AU - Bolton, Adam S.
AU - Schlegel, David J.
AU - Aubourg, Eric
AU - Bailey, Stephen
AU - Bhardwaj, Vaishali
AU - Brownstein, Joel R.
AU - Burles, Scott
AU - Chen, Yan-Mei
AU - Dawson, Kyle
AU - Eisenstein, Daniel J.
AU - Gunn, James E.
AU - Knapp, G. R.
AU - Loomis, Craig P.
AU - Lupton, Robert H.
AU - Maraston, Claudia
AU - Muna, Demitri
AU - Myers, Adam D.
AU - Olmstead, Matthew D.
AU - Padmanabhan, Nikhil
AU - Paris, Isabelle
AU - Percival, Will J.
AU - Petitjean, Patrick
AU - Rockosi, Constance M.
AU - Ross, Nicholas P.
AU - Schneider, Donald P.
AU - Shu, Yiping
AU - Strauss, Michael A.
AU - Thomas, Daniel
AU - Tremonti, Christy A.
AU - Wake, David A.
AU - Weaver, Benjamin A.
AU - Wood-Vasey, W. Michael
PY - 2012/11
Y1 - 2012/11
N2 - 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 spectroscopicdata set and describe directions of ongoing development.
AB - 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 spectroscopicdata set and describe directions of ongoing development.
KW - methods: data analysis
KW - surveys
KW - techniques: spectroscopic
U2 - 10.1088/0004-6256/144/5/144
DO - 10.1088/0004-6256/144/5/144
M3 - Article
SN - 0004-6256
VL - 144
SP - 144
JO - The Astronomical Journal
JF - The Astronomical Journal
IS - 5
ER -