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A striking relationship between dust extinction and radio detection in DESI QSOs: evidence for a dusty blow-out phase in red QSOs

Lookup NU author(s): Dr Vicky FawcettORCiD, Dr David Rosario, Dr Christopher HarrisonORCiD


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© 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.We present the first eight months of data from our secondary target programme within the ongoing Dark Energy Spectroscopic Instrument (DESI) survey. Our programme uses a mid-infrared and optical colour selection to preferentially target dust-reddened quasi-stellar objects (QSOs) that would have otherwise been missed by the nominal DESI QSO selection. So far, we have obtained optical spectra for 3038 candidates, of which ∼70 per cent of the high-quality objects (those with robust redshifts) are visually confirmed to be Type 1 QSOs, consistent with the expected fraction from the main DESI QSO survey. By fitting a dust-reddened blue QSO composite to the QSO spectra, we find they are well-fitted by a normal QSO with up to AV ∼4 mag of line-of-sight dust extinction. Utilizing radio data from the LOFAR Two-metre Sky Survey (LoTSS) DR2, we identify a striking positive relationship between the amount of line-of-sight dust extinction towards a QSO and the radio detection fraction, that is not driven by radio-loud systems, redshift and/or luminosity effects. This demonstrates an intrinsic connection between dust reddening and the production of radio emission in QSOs, whereby the radio emission is most likely due to low-powered jets or winds/outflows causing shocks in a dusty environment. On the basis of this evidence, we suggest that red QSOs may represent a transitional 'blow-out' phase in the evolution of QSOs, where winds and outflows evacuate the dust and gas to reveal an unobscured blue QSO.

Publication metadata

Author(s): Fawcett VA, Alexander DM, Brodzeller A, Edge AC, Rosario DJ, Myers AD, Aguilar J, Ahlen S, Alfarsy R, Brooks D, Canning R, Circosta C, Dawson K, De La Macorra A, Doel P, Fanning K, Font-Ribera A, Forero-Romero JE, Gontcho SGA, Guy J, Harrison CM, Honscheid K, Juneau S, Kehoe R, Kisner T, Kremin A, Landriau M, Manera M, Meisner AM, Miquel R, Moustakas J, Nie J, Percival WJ, Poppett C, Pucha R, Rossi G, Schlegel D, Siudek M, Tarle G, Weaver BA, Zhou Z, Zou H

Publication type: Article

Publication status: Published

Journal: Monthly Notices of the Royal Astronomical Society

Year: 2023

Volume: 525

Issue: 4

Pages: 5575-5596

Print publication date: 01/11/2023

Online publication date: 13/09/2023

Acceptance date: 24/08/2023

ISSN (print): 0035-8711

ISSN (electronic): 1365-2966

Publisher: Oxford University Press


DOI: 10.1093/mnras/stad2603


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