The LOFAR Two-metre Sky Survey Deep Fields

Astronomy and Astrophysics, vol. 656, pp. A48

Abstract

We have exploited LOFAR deep observations of the Lockman Hole field at 150 MHz to investigate the relation between the radio luminosity of star-forming galaxies (SFGs) and their star-formation rates (SFRs), as well as its dependence on stellar mass and redshift. The adopted source classification, SFRs, and stellar masses are consensus estimates based on a combination of four different spectral energy distribution fitting methods. We note a flattening of the radio spectra of a substantial minority of sources below ∼1.4 GHz. Such sources have thus a lower ‘radio-loudness’ level at 150 MHz than expected from extrapolations from 1.4 GHz using the average spectral index. We found a weak trend towards a lower SFR/L150 MHzratio for higher stellar mass,M⋆. We argue that such a trend may account for most of the apparent redshift evolution of theL150 MHz/SFR ratio, in line with previous work. Our data indicate a weaker evolution than found by some previous analyses. We also find a weaker evolution with redshift of the specific SFR than found by several (but not all) previous studies. Our radio selection provides a view of the distribution of galaxies in the SFR–M⋆plane complementary to that of optical and near-IR selection. It suggests a higher uniformity of the star-formation history of galaxies than implied by some analyses of optical and near-IR data. We have derived luminosity functions at 150 MHz of both SFGs and radio-quiet (RQ) AGN at various redshifts. Our results are in very good agreement with the T-RECS simulations and with literature estimates. We also present explicit estimates of SFR functions of SFGs and RQ AGN at several redshifts derived from our radio survey data.

Authors 17

1. Matteo Bonato

   Istituto di Radioastronomia di Bologna · Osservatorio Astronomico di Padova · National Institute for Astrophysics

   Affiliation as printed

   INAF-Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy

   INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy

   Italian ALMA Regional Centre, Via Gobetti 101, 40129 Bologna, Italy

   INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy

2. Isabella Prandoni

   Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

   Affiliation as printed

   INAF-Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy

3. G. de Zotti

   Osservatorio Astronomico di Padova · National Institute for Astrophysics

   Affiliation as printed

   INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy

   INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy

4. P. N. Best

   Royal Observatory

   Affiliation as printed

   SUPA, Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK

5. M. Bondi

   Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

   Affiliation as printed

   INAF-Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy

6. G. Calistro Rivera

   European Southern Observatory

   Affiliation as printed

   European Southern Observatory, Karl-Schwarzchild-Strasse 2, 85748 Garching bei München, Germany

7. R. K. Cochrane

   Center for Astrophysics Harvard & Smithsonian

   Affiliation as printed

   Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA

8. G. Gürkan

   Thüringer Landessternwarte Tautenburg

   Affiliation as printed

   Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany

9. P. Haskell

   University of Hertfordshire

   Affiliation as printed

   Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB, UK

10. R. Kondapally

    Royal Observatory

    Affiliation as printed

    SUPA, Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK

11. M. Magliocchetti

    Institute for Space Astrophysics and Planetology · National Institute for Astrophysics

    Affiliation as printed

    INAF-Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, 00133 Roma, Italy

12. S. K. Leslie Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands

13. K. Małek

    Centre National de la Recherche Scientifique · Aix-Marseille Université · National Centre for Nuclear Research

    Affiliation as printed

    Aix Marseille Univ. CNRS, CNES, LAM, Marseille, France

    National Centre for Nuclear Research, ul. Pasteura 7, 02-093 Warszawa, Poland

14. Huub J. A. Röttgering Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands

15. Daniel J. B. Smith

    University of Hertfordshire

    Affiliation as printed

    Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB, UK

16. Cyril Tasse

    Centre National de la Recherche Scientifique · Rhodes University · Observatoire de Paris · Galaxies, Etoiles, Physique et Instrumentation · Université Paris Diderot

    Affiliation as printed

    Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa

    GEPI & USN, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France

17. Lingyu Wang Aachen SRON Netherlands Institute for Space Research

    University of Groningen · Space Research Organisation Netherlands

    Affiliation as printed

    Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands

    SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands