dc.contributor.author Mooney, S. dc.contributor.author Quinn, J. dc.contributor.author Callingham, J. R. dc.contributor.author Morganti, R. dc.contributor.author Duncan, K. dc.contributor.author Morabito, Leah K. dc.contributor.author Best, P. N. dc.contributor.author Gürkan, G. dc.contributor.author Hardcastle, M. J. dc.contributor.author Prandoni, I. dc.contributor.author Röttgering, H. J. A. dc.contributor.author Sabater, J. dc.contributor.author Shimwell, T. W. dc.contributor.author Shulevski, A. dc.contributor.author Tasse, C. dc.contributor.author Williams, W. L. dc.date.accessioned 2019-01-10T14:30:17Z dc.date.available 2019-01-10T14:30:17Z dc.date.issued 2018-11-19 dc.identifier.citation Mooney , S , Quinn , J , Callingham , J R , Morganti , R , Duncan , K , Morabito , L K , Best , P N , Gürkan , G , Hardcastle , M J , Prandoni , I , Röttgering , H J A , Sabater , J , Shimwell , T W , Shulevski , A , Tasse , C & Williams , W L 2018 , ' Blazars in the LOFAR Two-Metre Sky Survey First Data Release ' , Astronomy & Astrophysics . https://doi.org/10.1051/0004-6361/201833937 dc.identifier.issn 0004-6361 dc.identifier.other PURE: 15717725 dc.identifier.other PURE UUID: 2778bfa6-89c0-4dea-be4a-4bb8922dfbec dc.identifier.other ArXiv: http://arxiv.org/abs/1811.07961v1 dc.identifier.uri http://hdl.handle.net/2299/20951 dc.description 7 figures, 6 tables and 11 pages. 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. © 2019 ESO dc.description.abstract Historically, the blazar population has been poorly understood at low frequencies because survey sensitivity and angular resolution limitations have made it difficult to identify megahertz counterparts. We used the LOFAR Two-Metre Sky Survey (LoTSS) first data release value-added catalogue (LDR1) to study blazars in the low-frequency regime with unprecedented sensitivity and resolution. We identified radio counterparts to all $98$ known sources from the Third \textit{Fermi}-LAT Point Source Catalogue (3FGL) or Roma-BZCAT Multi-frequency Catalogue of Blazars ($5^{\mathrm{th}}$ edition) that fall within the LDR1 footprint. Only the 3FGL unidentified $\gamma$-ray sources (UGS) could not be firmly associated with an LDR1 source; this was due to source confusion. We examined the redshift and radio luminosity distributions of our sample, finding flat-spectrum radio quasars (FSRQs) to be more distant and more luminous than BL Lacertae objects (BL Lacs) on average. Blazars are known to have flat spectra in the gigahertz regime but we found this to extend down to $144$ MHz, where the radio spectral index, $\alpha$, of our sample is $-0.17 \pm 0.14$. For BL Lacs, $\alpha = -0.13 \pm 0.16$ and for FSRQs, $\alpha = -0.15 \pm 0.17$. We also investigated the radio-to-$\gamma$-ray connection for the $30$ $\gamma$-ray-detected sources in our sample. We find Pearson's correlation coefficient is $0.45$ ($p = 0.069$). This tentative correlation and the flatness of the spectral index suggest that the beamed core emission contributes to the low-frequency flux density. We compare our sample distribution with that of the full LDR1 on colour-colour diagrams, and we use this information to identify possible radio counterparts to two of the four UGS within the LDR1 field. We will refine our results as LoTSS continues. en dc.language.iso eng dc.relation.ispartof Astronomy & Astrophysics dc.rights /dk/atira/pure/core/openaccesspermission/open dc.subject astro-ph.HE dc.title Blazars in the LOFAR Two-Metre Sky Survey First Data Release 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 2018-11-18 rioxxterms.version AM rioxxterms.versionofrecord https://doi.org/10.1051/0004-6361/201833937 rioxxterms.type Journal Article/Review herts.preservation.rarelyaccessed true herts.rights.accesstype openAccess
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