XQ-100: A legacy survey of one hundred 3.5 ≲ z ≲ 4.5 quasars observed with VLT/X-shooter^⋆,⋆⋆

¹ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
e-mail: slopez@das.uchile.cl
² INAF–Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
³ Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1, Canada
⁴ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁵ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
⁶ Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
⁷ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁸ INFN / National Institute for Nuclear Physics, via Valerio 2, 34127 Trieste, Italy
⁹ Observatoire de Genève, Université de Genève, 51, Ch. des Maillettes, 1290 Sauverny, Switzerland
¹⁰ Institute of Astronomy and Kavli Institute of Cosmology, Madingley Road, Cambridge CB3 0HA, UK
¹¹ Department of Astronomy, University of Florida, Gainesville, FL 32611-2055, USA
¹² International Center for Theoretical Physics (ICTP), Strada Costiera 11, 34151 Trieste, Italy
¹³ Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
¹⁴ International School for Advanced Studies (SISSA) via Bonomea 265, 34136 Trieste, Italy
¹⁵ Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064, USA
¹⁶ Unidad Asociada Grupo Ciencias Planetarias (UPV/EHU, IAA-CSIC), Departamento de Física Aplicada I, E.T.S. Ingeniería, Universidad del País Vasco (UPV/EHU), Alameda de Urquijo s/n, 48013 Bilbao, Spain
¹⁷ Ikerbasque, Basque Foundation for Science, Alameda de Urquijo 36-5, 48008 Bilbao, Spain
¹⁸ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008, Granada, Spain
¹⁹ Department of Astronomy and Steward Observatory University of Arizona, 933 N Cherry Avenue Tucson AZ 85721, USA
²⁰ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

Received: 19 January 2016
Accepted: 22 July 2016

Abstract

We describe the execution and data reduction of the European Southern Observatory Large Programme “Quasars and their absorption lines: a legacy survey of the high-redshift Universe with VLT/X-shooter” (hereafter “XQ-100”). XQ-100 has produced and made publicly available a homogeneous and high-quality sample of echelle spectra of 100 quasars (QSOs) at redshifts z ≃ 3.5–4.5 observed with full spectral coverage from 315 to 2500 nm at a resolving power ranging from R ~ 4000 to 7000, depending on wavelength. The median signal-to-noise ratios are 33, 25 and 43, as measured at rest-frame wavelengths 1700, 3000 and 3600 Å, respectively. This paper provides future users of XQ-100 data with the basic statistics of the survey, along with details of target selection, data acquisition and data reduction. The paper accompanies the public release of all data products, including 100 reduced spectra. XQ-100 is the largest spectroscopic survey to date of high-redshift QSOs with simultaneous rest-frame UV/optical coverage, and as such enables a wide range of extragalactic research, from cosmology and galaxy evolution to AGN astrophysics.