Repository logo

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

Accepted version



Change log


López, S 
D'Odorico, V 
Ellison, SL 
Becker, GD 
Christensen, L 


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/XSHOOTER" (hereafter `XQ-100'). XQ-100 has produced and made publicly available an homogeneous and high-quality sample of echelle spectra of 100 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 Angstrom, 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.



surveys, quasars: general

Journal Title

Astronomy and Astrophysics

Conference Name

Journal ISSN


Volume Title


EDP Sciences
European Research Council (320596)
Science and Technology Facilities Council (ST/N000927/1)
SL has been supported by FONDECYT grant number 1140838 and partially by PFB-06 CATA. VD, IP, and SP acknowledge support from the PRIN INAF 2012 “The X-Shooter sample of 100 quasar spectra at z ∼ 3.5: Digging into cosmology and galaxy evolution with quasar absorption lines”. SLE acknowledges the receipt of an NSERC Discovery Grant. MH acknowledges support by ERC ADVANCED GRANT 320596 “The Emergence of Structure during the epoch of Reionization”. The Dark Cosmology Centre is funded by the Danish National Research Foundation. MVe gratefully acknowledges support from the Danish Council for Independent Research via grant no. DFF – 4002-00275. MV is supported by ERC-StG “cosmoIGM”. KDD is supported by an NSF AAPF fellowship awarded under NSF grant AST-1302093. TSK acknowledges funding support from the European Research Council Starting Grant “Cosmology with the IGM” through grant GA- 257670. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England.