Using strong lensing to understand the microJy radio emission in two radio quiet quasars at redshift 1.7
Abstract
The radio quasar luminosity function exhibits an upturn around $L_{6\rm \:GHz}=10^{23}$ W Hz-1 that is well-modelled by a star-forming host galaxy population. This distribution leads some authors to cite star formation as the main radio emission mechanism in so-called radio-quiet quasars (RQQs). Understanding the origin of RQQ radio emission is crucial for our understanding of quasar feedback mechanisms - responsible for the regulation of star formation in the host galaxy - and for understanding galaxy evolution as a whole. By observing RQQs that have been magnified by strong gravitational lensing, we have direct access to the RQQ population out to cosmic noon, where evidence for twin mini-jets has recently been found in a sub-$\mu$Jy RQQ. Here we present radio observations of two lensed RQQs using the VLA at 5 GHz, the latest objects to be observed in a sample of quadruply-imaged RQQs above -30°. In SDSS J1004+4112 we find strong evidence for AGN-related radio emission in the variability of the source. In PG 1115+080 we find tentative evidence for AGN-related emission, determined by comparing the radio luminosity with modelled dust components. If confirmed in the case of PG 1115+080, which lies on the radio-FIR correlation, the result would reinforce the need for caution when applying the correlation to rule out jet activity and when assuming no AGN heating of FIR-emitting dust when calculating star formation rates. Our programme so far has shown that the two of the faintest radio sources ever imaged show strong evidence for AGN-dominated radio emission.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2021
- DOI:
- arXiv:
- arXiv:2109.10720
- Bibcode:
- 2021MNRAS.508.4625H
- Keywords:
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- gravitational lensing: strong;
- galaxies: active;
- quasars: general;
- galaxies: individual: SDSS J1004+4112;
- galaxies: individual: PG 1115+080;
- galaxies: star formation;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted by MNRAS