The Prism Multi-Object Survey (Primus). I. Survey Overview and Characteristics

We present the PRIsm MUlti-object Survey (PRIMUS), a spectroscopic faint galaxy redshift survey to z ∼ 1. PRIMUS uses a low-dispersion prism and slitmasks to observe ∼2500 objects at once in a 0.18 deg 2 field of view, using the Inamori Magellan Areal Camera and Spectrograph camera on the Magellan I Baade 6.5 m telescope at Las Campanas Observatory. PRIMUS covers a total of 9.1 deg 2 of sky to a depth of i AB ∼ 23.5 in seven different deep, multi-wavelength fields that have coverage from the Galaxy Evolution Explorer , Spitzer , and either XMM or Chandra , as well as multiple-band optical and near-IR coverage. PRIMUS includes ∼130,000 robust redshifts of unique objects with a redshift precision of σ z /(1 + z ) ∼ 0.005. The redshift distribution peaks at z ∼ 0.6 and extends to z = 1.2 for galaxies and z = 5 for broad-line active galactic nuclei. The motivation, observational techniques, fields, target selection, slitmask design, and observations are presented here, with a brief summary of the redshift precision; a forthcoming paper presents the data reduction, redshift fitting, redshift confidence, and survey completeness. PRIMUS is the largest faint galaxy survey undertaken to date. The high targeting fraction (∼80%) and large survey size will allow for precise measures of galaxy properties and large-scale structure to z ∼ 1.