The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1

III. Host-galaxy identifications and value added catalogues^★,★★

¹ SUPA, Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
e-mail: rohitk@roe.ac.uk
² Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
³ INAF – Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
⁴ Italian ALMA Regional Centre, Via Gobetti 101, 40129 Bologna, Italy
⁵ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁶ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁷ Astronomy Centre, Department of Physics & Astronomy, University of Sussex, Brighton, BN1 9QH, England, UK
⁸ Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA
⁹ Astrophysics, University of Oxford, Keble Road, Oxford, OX1 3RH, UK
¹⁰ ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands
¹¹ GEPI, Observatoire de Paris, CNRS, Universite Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
¹² Department of Physics & Electronics, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
¹³ School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
¹⁴ Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30–244 Kraków, Poland
¹⁵ Department of Physics & Astronomy, University of the Western Cape, Private Bag X17, Bellville, Cape Town 7535, South Africa
¹⁶ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, NCU, Grudziadzka 5, 87-100 Toruń, Poland
¹⁷ Dipartimento di Fisica e Astronomia, Università di Bologna, Via P. Gobetti 93/2, 40129 Bologna, Italy
¹⁸ School of Physics and Astronomy, Monash University, Clayton, Victoria 3800, Australia
¹⁹ Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
²⁰ Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA
²¹ Jodrell Bank Centre for Astrophysics, University of Manchester, Alan Turing Building, Oxford Road, M13 9PL, UK
²² CSIRO Astronomy and Space Science, PO Box 1130, Bentley WA 6102, Australia
²³ School of Physical Sciences and Centre for Astrophysics & Relativity, Dublin City University, Glasnevin, D09 W6Y4, Ireland
²⁴ Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany
²⁵ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam, The Netherlands
²⁶ Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
²⁷ SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD, Groningen, The Netherlands
²⁸ Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands

Received: 1 July 2020
Accepted: 26 October 2020

Abstract

We present the source associations, cross-identifications, and multi-wavelength properties of the faint radio source population detected in the deep tier of the LOFAR Two Metre Sky Survey (LoTSS): the LoTSS Deep Fields. The first LoTSS Deep Fields data release consists of deep radio imaging at 150 MHz of the ELAIS-N1, Lockman Hole, and Boötes fields, down to RMS sensitives of around 20, 22, and 32 μJy beam⁻¹, respectively. These fields are some of the best studied extra-galactic fields in the northern sky, with existing deep, wide-area panchromatic photometry from X-ray to infrared wavelengths, covering a total of ≈26 deg². We first generated improved multi-wavelength catalogues in ELAIS-N1 and Lockman Hole; combined with the existing catalogue for Boötes, we present forced, matched aperture photometry for over 7.2 million sources across the three fields. We identified multi-wavelength counterparts to the radio detected sources, using a combination of the Likelihood Ratio method and visual classification, which greatly enhances the scientific potential of radio surveys and allows for the characterisation of the photometric redshifts and the physical properties of the host galaxies. The final radio-optical cross-matched catalogue consists of 81 951 radio-detected sources, with counterparts identified and multi-wavelength properties presented for 79 820 (>97%) sources. We also examine the properties of the host galaxies, and through stacking analysis find that the radio population with no identified counterpart is likely dominated by active galactic nuclei (AGN) at z ~ 3−4. This dataset contains one of the largest samples of radio-selected star-forming galaxies and AGN at these depths, making it ideal for studying the history of star-formation, and the evolution of galaxies and AGN across cosmic time.