dc.contributor.author Gürkan, Gülay dc.contributor.author Hardcastle, Martin dc.contributor.author Best, Philip dc.contributor.author Morabito, Leah dc.contributor.author Prandoni, Isabella dc.contributor.author Jarvis, Matt dc.contributor.author Duncan, Ken dc.contributor.author Rivera, Gabriela Calistro dc.contributor.author Callingham, Joe dc.contributor.author Cochrane, Rachel dc.contributor.author Croston, Judith dc.contributor.author Heald, George dc.contributor.author Mingo, Beatriz dc.contributor.author Mooney, Sean dc.contributor.author Sabater, Jose dc.contributor.author Röttgering, Huub dc.contributor.author Shimwell, Timothy dc.contributor.author Smith, Dan dc.contributor.author Tasse, Cyril dc.contributor.author Williams, Wendy dc.date.accessioned 2019-01-17T16:45:07Z dc.date.available 2019-01-17T16:45:07Z dc.date.issued 2018-10-10 dc.identifier.citation Gürkan , G , Hardcastle , M , Best , P , Morabito , L , Prandoni , I , Jarvis , M , Duncan , K , Rivera , G C , Callingham , J , Cochrane , R , Croston , J , Heald , G , Mingo , B , Mooney , S , Sabater , J , Röttgering , H , Shimwell , T , Smith , D , Tasse , C & Williams , W 2018 , ' LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars ' , Astronomy & Astrophysics . https://doi.org/10.1051/0004-6361/201833892 dc.identifier.issn 0004-6361 dc.identifier.other PURE: 15717838 dc.identifier.other PURE UUID: bf3d421e-f5de-41bb-b192-f91db8f3c11d dc.identifier.other ArXiv: http://arxiv.org/abs/1811.07933v1 dc.identifier.other Scopus: 85062044329 dc.identifier.uri http://hdl.handle.net/2299/20989 dc.description 16 pages, 12 figures, 4 tables. This paper is part of the LOFAR surveys data release 1 and has been accepted for publication in a special edition of A&A that will appear in Feb 2019, volume 622. The catalogues and images from the data release will be publicly available on lofar-surveys.org upon publication of the journal. Reproduced with permission from Astronomy & Astrophysics. © 2018 ESO. dc.description.abstract The radio-loud/radio-quiet (RL/RQ) dichotomy in quasars is still an open question. Although it is thought that accretion onto supermassive black holes in the centre the host galaxies of quasars is responsible for some radio continuum emission, there is still a debate as to whether star formation or active galactic nuclei (AGN) activity dominate the radio continuum luminosity. To date, radio emission in quasars has been investigated almost exclusively using high-frequency observations in which the Doppler boosting might have an important effect on the measured radio luminosity, whereas extended structures, best observed at low radio frequencies, are not affected by the Doppler enhancement. We used a sample of quasars selected by their optical spectra in conjunction with sensitive and high-resolution low-frequency radio data provided by the LOw Frequency ARray (LOFAR) as part of the LOFAR Two-Metre Sky Survey (LoTSS) to investigate their radio properties using the radio loudness parameter ($\mathcal{R} = \frac{L_{\mathrm{144-MHz}}}{L_{\mathrm{i\,band}}}$). The examination of the radio continuum emission and RL/RQ dichotomy in quasars exhibits that quasars show a wide continuum of radio properties (i.e. no clear bimodality in the distribution of $\mathcal{R}$). Radio continuum emission at low frequencies in low-luminosity quasars is consistent with being dominated by star formation. We see a significant albeit weak dependency of $\mathcal{R}$ on the source nuclear parameters. For the first time, we are able to resolve radio morphologies of a considerable number of quasars. All these crucial results highlight the impact of the deep and high-resolution low-frequency radio surveys that foreshadow the compelling science cases for the Square Kilometre Array (SKA). en dc.language.iso eng dc.relation.ispartof Astronomy & Astrophysics dc.rights Open dc.subject astro-ph.GA dc.title LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars en dc.contributor.institution School of Physics, Astronomy and Mathematics dc.contributor.institution Centre for Astrophysics Research dc.description.status Peer reviewed dc.relation.school School of Physics, Astronomy and Mathematics dc.description.versiontype Final Accepted Version dcterms.dateAccepted 2018-10-10 rioxxterms.version AM rioxxterms.versionofrecord https://doi.org/10.1051/0004-6361/201833892 rioxxterms.licenseref.uri Other rioxxterms.type Journal Article/Review herts.preservation.rarelyaccessed true herts.rights.accesstype Open
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