z-GAL: A NOEMA spectroscopic redshift survey of bright Herschel galaxies

I. Overview

¹ Sorbonne Université, UPMC Université Paris 6 and CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
e-mail: cox@iap.fr
² Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38400 Saint-Martin-d’Hères, France
³ Aix-Marseille Université, CNRS and CNES, Laboratoire d’Astrophysique de Marseille, 38 rue Frédéric Joliot-Curie, 13388 Marseille, France
⁴ Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019, USA
⁵ Cosmic DAWN Center, Radmandsgade 62, 2200 Copenhagen N, Denmark
⁶ DTU Space, Technical University of Denmark, Elektrovej 327, 2800 Kgs Lyngby, Denmark
⁷ Departement of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
⁸ Division of Particle and Astrophysical Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
⁹ National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁰ Instituto Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
¹¹ Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, Spain
¹² Centre de Recherche Astrophysique de Lyon – CRAL, CNRS UMR 5574, UCBL1, ENS Lyon, 9 avenue Charles André, 69230 Saint-Genis-Laval, France
¹³ I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
¹⁴ Department of Physics and Astronomy, University of the Western Cape, Robert Sobukwe Road, Bellville, 7535 Cape Town, South Africa
¹⁵ UK ALMA Regional Center Node, Jodrell Bank Center for Astrophysics, Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
¹⁶ Dipartimento di Fisica & Astronomia “G. Galilei”, Università di Padova, vicolo dell’Osservatorio 3, Padova 35122, Italy
¹⁷ University of California Irvine, Department of Physics & Astronomy, FRH 2174, Irvine, CA 92697, USA
¹⁸ School of Physics and Astronomy, University of Nottingham, University Park, Notthingham NG7 2RD, UK
¹⁹ School of Physics and Astronomy, Cardiff University, Queens Building, The Parade, Cardiff CF24 3AA, UK
²⁰ Instituto Nacional de Astrofísica, Óptica y Electrónica, Astrophysics Department, Apdo 51 y 216, Tonantzintla, Puebla 72000, Mexico
²¹ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
²² Department of Physics and Astronomy, Macquarie University, North Ryde, New South Wales, Australia
²³ School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin D02 XF86, Ireland
²⁴ Institut for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
²⁵ Departement of Astronomy, University of Cape Town, 7701 Rondebosch, Cape Town, South Africa
²⁶ Istituto Nazionale di Astrofisica, Istituto di Radioastronomia – Italian ARC, Via Piero Gobetti 101, 40129 Bologna, Italy
²⁷ Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, 763-0355 Santiago de Chile, Chile
²⁸ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla, 19001 Santiago de Chile, Chile
²⁹ National Centre for Nuclear Research, ul. Pasteura 7, 02-093 Warsaw, Poland
³⁰ INAF – Osservatorio astronomico d’Abruzzo, Via Maggini, SNC, 64100 Teramo, Italy
³¹ Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
³² National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
³³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
³⁴ Leiden University, Leiden Observatory, PO Box 9513, 2300 RA, Leiden, The Netherlands

Received: 3 May 2023
Accepted: 10 July 2023

Abstract

Using the IRAM NOrthern Extended Millimetre Array (NOEMA), we conducted a Large Programme (z-GAL) to measure redshifts for 126 bright galaxies detected in the Herschel Astrophysical Large Area Survey (H-ATLAS), the HerMES Large Mode Survey (HeLMS), and the Herschel Stripe 82 (HerS) Survey. We report reliable spectroscopic redshifts for a total of 124 of the Herschel-selected galaxies. The redshifts are estimated from scans of the 3 and 2-mm bands (and, for one source, the 1-mm band), covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. Together with the Pilot Programme, where 11 sources had their spectroscopic redshifts measured, our survey has derived precise redshifts for 135 bright Herschel-selected galaxies, making it the largest sample of high-z galaxies with robust redshifts to date. Most emission lines detected are from ¹²CO (mainly from J = 2–1 to 5–4), with some sources seen in [CI] and H₂O emission lines. The spectroscopic redshifts are in the range 0.8 < z < 6.55 with a median value of z = 2.56 ± 0.10, centred on the peak epoch of galaxy formation. The linewidths of the sources are large, with a mean value for the full width at half maximum ΔV of 590 ± 25 km s⁻¹ and with 35% of the sources having widths of 700 km s⁻¹ < ΔV < 1800 km s⁻¹. Most of the sources are unresolved or barely resolved on scales of ∼2 to 3″ (or linear sizes of ∼15 − 25 kpc, unlensed). Some fields reveal double or multiple sources in line emission and the underlying dust continuum and, in some cases, sources at different redshifts. Taking these sources into account, there are, in total, 165 individual sources with robust spectroscopic redshifts, including lensed galaxies, binary systems, and over-densities. This paper presents an overview of the z-GAL survey and provides the observed properties of the emission lines, the derived spectroscopic redshifts, and a catalogue of the entire sample. The catalogue includes, for each source, the combined continuum and emission lines’ maps together with the spectra for each of the detected emission lines. The data presented here will serve as a foundation for the other z-GAL papers in this series reporting on the dust emission, the molecular and atomic gas properties, and a detailed analysis of the nature of the sources. Comparisons are made with other spectroscopic surveys of high-z galaxies and future prospects, including dedicated follow-up observations based on these redshift measurements, are outlined.