Date Published:

March 1, 2012

Abstract:

The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-yearspectroscopic survey of 10,000 deg², achieved first light inlate 2009. One of the key goals of BOSS is to measure the signature ofbaryon acoustic oscillations (BAOs) in the distribution of Lyαabsorption from the spectra of a sample of ~150,000 z > 2.2 quasars.Along with measuring the angular diameter distance at z ≈ 2.5, BOSSwill provide the first direct measurement of the expansion rate of theuniverse at z > 2. One of the biggest challenges in achieving thisgoal is an efficient target selection algorithm for quasars in theredshift range 2.2 < z < 3.5, where their colors tend to overlapthose of the far more numerous stars. During the first year of the BOSSsurvey, quasar target selection (QTS) methods were developed and testedto meet the requirement of delivering at least 15 quasarsdeg^-2 in this redshift range, with a goal of 20 out of 40targets deg^-2 allocated to the quasar survey. To achievethese surface densities, the magnitude limit of the quasar targets wasset at g <= 22.0 or r <= 21.85. While detection of the BAOsignature in the distribution of Lyα absorption in quasar spectradoes not require a uniform target selection algorithm, many otherastrophysical studies do. We have therefore defined a uniformly selectedsubsample of 20 targets deg^-2, for which the selection

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