The radio loudness of SDSS quasars from the LOFAR Two-metre Sky Survey: ubiquitous jet activity and constraints on star formation

Journal Article · 15 July 2021 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stab1998 · OSTI ID:1813093

Macfarlane, C. ^[1]; Best, P. N. ^[1]; Sabater, J. ^[2]; Gürkan, G.  ^[3]; Jarvis, M. J.  ^[4]; Röttgering, H. J. A. ^[5]; Baldi, R. D.  ^[6]; Calistro Rivera, G.  ^[7]; Duncan, K. J.  ^[8]; Morabito, L. K.  ^[9]; Prandoni, I.  ^[10]; Retana-Montenegro, E. ^[11]

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1. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
2. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK, UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
3. Thüringer Landessternwarte, Sternwarte 5, D-07778 Tautenburg, Germany, CSIRO Astronomy and Space Science, PO Box 1130, Bentley, WA 6102, Australia
4. Astrophysics, Department of Physics,University of Oxford, Keble Road, Oxford OX1 3RH, UK, Department of Physics & Astronomy, University of the Western Cape, Private Bag X17, Bellville, Cape Town 7535, South Africa
5. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
6. INAF – Istituto di Radioastronomia, Via Piero Gobetti 101, I-40129 Bologna, Italy, Department of Physics & Astronomy, University of Southampton, Hampshire, Southampton SO17 1BJ, UK
7. European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching bei München, Germany
8. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK, Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
9. Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham DH1 3LE, UK
10. INAF – Istituto di Radioastronomia, Via Piero Gobetti 101, I-40129 Bologna, Italy
11. Astrophysics & Cosmology Research Unit, School of Mathematics, Statistics & Computer Science, University of KwaZulu-Natal, Durban 4041, South Africa

ABSTRACT We examine the distribution of radio emission from ∼42 000 quasars from the Sloan Digital Sky Survey, as measured in the LOFAR Two-metre Sky Survey (LoTSS). We present a model of the radio luminosity distribution of the quasars that assumes that every quasar displays a superposition of two sources of radio emission: active galactic nuclei (jets) and star formation. Our two-component model provides an excellent match to the observed radio flux density distributions across a wide range of redshifts and quasar optical luminosities; this suggests that the jet-launching mechanism operates in all quasars but with different powering efficiency. The wide distribution of jet powers allows for a smooth transition between the ‘radio-quiet’ and ‘radio-loud’ quasar regimes, without need for any explicit bimodality. The best-fitting model parameters indicate that the star formation rate of quasar host galaxies correlates strongly with quasar luminosity and also increases with redshift at least out to z ∼ 2. For a model where star formation rate scales as $$L_{\rm bol}^{\alpha } (1+z)^{\beta }$$, we find α = 0.47 ± 0.01 and β = 1.61 ± 0.05, in agreement with far-infrared studies. Quasars contribute ≈0.15 per cent of the cosmic star formation rate density at z = 0.5, rising to 0.4 per cent by z ∼ 2. The typical radio jet power is seen to increase with both increasing optical luminosity and black hole mass independently, but does not vary with redshift, suggesting intrinsic properties govern the production of the radio jets. We discuss the implications of these results for the triggering of quasar activity and the launching of jets.

• Research Organization: US Department of Energy (USDOE), Washington, DC (United States). Office of Science, Sloan Digital Sky Survey (SDSS)
• Sponsoring Organization: USDOE
• Contributing Organization: Sloan Digital Sky Survey (SDSS)
• OSTI ID: 1813093
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 4 Vol. 506; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English