The VANDELS ESO public spectroscopic survey: Observations and first data release

¹ INAF-Osservatorio Astronomico di Roma, via Frascati 33, 00078 Monteporzio Catone, Italy
e-mail: laura.pentericci@oa-roma.inaf.it
² Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK
³ INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via Bassini 15, 20133 Milano, Italy
⁴ INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
⁵ INAF-Osservatorio Astronomico di Brera, via Brera 28, 20122 Milano, Italy
⁶ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁷ Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge CB3 0HE, UK
⁸ Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Via Piero Gobetti 93/2, 40129 Bologna, Italy
⁹ INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50157 Firenze, Italy
¹⁰ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching b. München, Germany
¹¹ Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
¹² Laboratoire AIM Paris-Saclay, CEA/DSM/Irfu, CNRS, 91191 Gifsur-Yvette, France
¹³ Department of Astronomy, The University of Texas at Austin, Austin, TX 78712, USA
¹⁴ INAF-Astronomical Observatory of Trieste, via G.B. Tiepolo 11, 34143 Trieste, Italy
¹⁵ Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ej’ercito 441, Santiago, Chile
¹⁶ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
¹⁷ Astrophysics, The Denys Wilkinson Building, University of Oxford, Keble Road, Oxford OX1 3RH, England
¹⁸ Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands
¹⁹ Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, Garching 85748, Germany
²⁰ European Southern Observatory, Avenida Alonso de Córdova 3107, Vitacura, 19001 Casilla, Santiago de Chile, Chile
²¹ School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
²² University Observatory Munich, Scheinerstrasse 1, 81679 Munich, Germany
²³ Department of Astronomy, University of Michigan, 311 West Hall, 1085 South University Ave., Ann Arbor, MI 48109-1107, USA
²⁴ Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa, OAL, Tapada da Ajuda, 1349-018 Lisbon, Portugal
²⁵ Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Edifício C8, Campo Grande, 1749-016 Lisbon, Portugal
²⁶ Instituto de Fisica y Astronomia, Facultad de Ciencias, Universidad de Valparaiso, 1111 Gran Bretana, Valparaiso, Chile
²⁷ Institute d’Astrophysique de Paris, CNRS, Université Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris, France
²⁸ National Optical Astronomy Observatory, 950 North Cherry Ave, Tucson, AZ 85719, USA
²⁹ Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge MA 20138, England
³⁰ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
³¹ The Cosmic Dawn Center, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
³² Astronomy Department, University of Massachusetts, Amherst, MA 01003, USA
³³ Instituto de Astrofísica Avda. Pontificia Universidad Católica de Chile, Vicuña Mackenna, 4860 Santiago, Chile
³⁴ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
³⁵ Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
³⁶ Departamento de Astrofísica, Universidad de La Laguna, 38200 La Laguna, Tenerife, Spain
³⁷ Faculty of Physics, Ludwig-Maximilians Universität, Scheinerstr. 1, 81679 Munich, Germany
³⁸ Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843-4242, USA
³⁹ Excellence Cluster, Boltzmannstr. 2, 85748 Garching, Germany
⁴⁰ Department of Physics, Durham University, South Road, DH1 3LE Durham, UK
⁴¹ Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
⁴² Steward Observatory, The University of Arizona, 933 N Cherry Ave, Tucson, AZ 85721, USA
⁴³ Department of Physics and Astronomy, PAB, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547, USA
⁴⁴ School of Physics and Astronomy, University of St. Andrews, SUPA, North Haugh, KY16 9SS St. Andrews, UK

Received: 19 March 2018
Accepted: 2 May 2018

Abstract

This paper describes the observations and the first data release (DR1) of the ESO public spectroscopic survey “VANDELS, a deep VIMOS survey of the CANDELS CDFS and UDS fields”. The main targets of VANDELS are star-forming galaxies at redshift 2.4 < z < 5.5, an epoch when the Universe had not yet reached 20% of its current age, and massive passive galaxies in the range 1 < z < 2.5. By adopting a strategy of ultra-long exposure times, ranging from a minimum of 20 h to a maximum of 80 h per source, VANDELS is specifically designed to be the deepest-ever spectroscopic survey of the high-redshift Universe. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the survey is obtaining ultra-deep optical spectroscopy covering the wavelength range 4800–10 000 Å with a sufficiently high signal-to-noise ratio to investigate the astrophysics of high-redshift galaxy evolution via detailed absorption line studies of well-defined samples of high-redshift galaxies. VANDELS-DR1 is the release of all medium-resolution spectroscopic data obtained during the first season of observations, on a 0.2 square degree area centered around the CANDELS-CDFS (Chandra deep-field south) and CANDELS-UDS (ultra-deep survey) areas. It includes data for all galaxies for which the total (or half of the total) scheduled integration time was completed. The DR1 contains 879 individual objects, approximately half in each of the two fields, that have a measured redshift, with the highest reliable redshifts reaching z_spec ~ 6. In DR1 we include fully wavelength-calibrated and flux-calibrated 1D spectra, the associated error spectrum and sky spectrum, and the associated wavelength-calibrated 2D spectra. We also provide a catalog with the essential galaxy parameters, including spectroscopic redshifts and redshift quality flags measured by the collaboration. We present the survey layout and observations, the data reduction and redshift measurement procedure, and the general properties of the VANDELS-DR1 sample. In particular, we discuss the spectroscopic redshift distribution and the accuracy of the photometricredshifts for each individual target category, and we provide some examples of data products for the various target typesand the different quality flags. All VANDELS-DR1 data are publicly available and can be retrieved from the ESO archive. Two further data releases are foreseen in the next two years, and a final data release is currently scheduled for June 2020, which will include an improved rereduction of the entire spectroscopic data set.