OzDES multifibre spectroscopy for the Dark Energy Survey: first-year operation and results

Abstract

OzDES is a five-year, 100-night, spectroscopic survey on the Anglo-Australian\nTelescope, whose primary aim is to measure redshifts of approximately 2,500\nType Ia supernovae host galaxies over the redshift range 0.1 < z < 1.2, and\nderive reverberation-mapped black hole masses for approximately 500 active\ngalactic nuclei and quasars over 0.3 < z < 4.5. This treasure trove of data\nforms a major part of the spectroscopic follow-up for the Dark Energy Survey\nfor which we are also targeting cluster galaxies, radio galaxies, strong\nlenses, and unidentified transients, as well as measuring luminous red galaxies\nand emission line galaxies to help calibrate photometric redshifts.\n Here we present an overview of the OzDES program and our first-year results.\nBetween Dec 2012 and Dec 2013, we observed over 10,000 objects and measured\nmore than 6,000 redshifts. Our strategy of retargeting faint objects across\nmany observing runs has allowed us to measure redshifts for galaxies as faint\nas m_r=25 mag. We outline our target selection and observing strategy, quantify\nthe redshift success rate for different types of targets, and discuss the\nimplications for our main science goals. Finally, we highlight a few\ninteresting objects as examples of the fortuitous yet not totally unexpected\ndiscoveries that can come from such a large spectroscopic survey.\n