# University of Hertfordshire

## Blazars in the LOFAR Two-Metre Sky Survey First Data Release

Research output: Contribution to journalArticle

### Standard

Blazars in the LOFAR Two-Metre Sky Survey First Data Release. / Mooney, S.; Quinn, J.; Callingham, J. R.; Morganti, R.; Duncan, K.; Morabito, Leah 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.

In: Astronomy & Astrophysics, 19.11.2018.

Research output: Contribution to journalArticle

### Harvard

Mooney, S, Quinn, J, Callingham, JR, Morganti, R, Duncan, K, Morabito, LK, Best, PN, Gürkan, G, Hardcastle, MJ, Prandoni, I, Röttgering, HJA, Sabater, J, Shimwell, TW, Shulevski, A, Tasse, C & Williams, WL 2018, 'Blazars in the LOFAR Two-Metre Sky Survey First Data Release', Astronomy & Astrophysics. https://doi.org/10.1051/0004-6361/201833937

### APA

Mooney, S., Quinn, J., Callingham, J. R., Morganti, R., Duncan, K., Morabito, L. K., ... 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

### Vancouver

Mooney S, Quinn J, Callingham JR, Morganti R, Duncan K, Morabito LK et al. Blazars in the LOFAR Two-Metre Sky Survey First Data Release. Astronomy & Astrophysics. 2018 Nov 19. https://doi.org/10.1051/0004-6361/201833937

### Author

Mooney, S. ; Quinn, J. ; Callingham, J. R. ; Morganti, R. ; Duncan, K. ; Morabito, Leah 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. / Blazars in the LOFAR Two-Metre Sky Survey First Data Release. In: Astronomy & Astrophysics. 2018.

### Bibtex

@article{2778bfa689c04deabe4a4bb8922dfbec,
title = "Blazars in the LOFAR Two-Metre Sky Survey First Data Release",
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.",
keywords = "astro-ph.HE",
author = "S. Mooney and J. Quinn and Callingham, {J. R.} and R. Morganti and K. Duncan and Morabito, {Leah K.} and Best, {P. N.} and G. G{\"u}rkan and Hardcastle, {M. J.} and I. Prandoni and R{\"o}ttgering, {H. J. A.} and J. Sabater and Shimwell, {T. W.} and A. Shulevski and C. Tasse and Williams, {W. L.}",
note = "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. {\circledC} 2019 ESO",
year = "2018",
month = "11",
day = "19",
doi = "10.1051/0004-6361/201833937",
language = "English",
journal = "Astronomy & Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",

}

### RIS

TY - JOUR

T1 - Blazars in the LOFAR Two-Metre Sky Survey First Data Release

AU - Mooney, S.

AU - Quinn, J.

AU - Callingham, J. R.

AU - Morganti, R.

AU - Duncan, K.

AU - Morabito, Leah K.

AU - Best, P. N.

AU - Gürkan, G.

AU - Hardcastle, M. J.

AU - Prandoni, I.

AU - Röttgering, H. J. A.

AU - Sabater, J.

AU - Shimwell, T. W.

AU - Shulevski, A.

AU - Tasse, C.

AU - Williams, W. L.

N1 - 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

PY - 2018/11/19

Y1 - 2018/11/19

N2 - 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.

AB - 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.

KW - astro-ph.HE

U2 - 10.1051/0004-6361/201833937

DO - 10.1051/0004-6361/201833937

M3 - Article

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

ER -