LoTSS/HETDEX: Disentangling star formation and AGN activity in gravitationally lensed radio-quiet quasars

¹ ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
e-mail: h.r.stacey@astro.rug.nl
² Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
³ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
⁴ SUPA, Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
⁵ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁶ CSIRO Astronomy and Space Science, PO Box 1130 Bentley WA 6102, Australia
⁷ Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB
⁸ Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁹ INAF – Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
¹⁰ GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 Place Jules Janssen, 92190 Meudon, France
¹¹ Department of Physics & Electronics, Rhodes University, PO Box 94 Grahamstown, 6140, South Africa

Received: 27 July 2018
Accepted: 30 October 2018

Abstract

Determining the star-forming properties of radio-quiet quasars is important for understanding the co-evolution of star formation and black hole accretion. We present the detection of the gravitationally lensed radio-quiet quasars SDSS J1055+4628, SDSS J1313+5151, and SBS 1520+530 at 144 MHz, which fall in the HETDEX Spring Field targeted in the LOFAR Two-metre Sky Survey (LoTSS) first full data release. We compare their radio and far-infrared luminosities relative to the radio–infrared correlation and find that their radio luminosities can be explained by star formation. The implied star formation rates derived from their radio and infrared luminosities are between 20 and 300 M _⊙ yr⁻¹. These detections represent the first study of gravitationally lensed sources with LOFAR, opening a new frequency window for investigating the star-forming properties of high-redshift quasars at radio wavelengths. We consider the implications for future data releases and estimate that many of the objects in our parent sample will be detected during LoTSS, significantly increasing the fraction of gravitationally lensed radio-quiet quasars with radio detections.