# University of Hertfordshire

## LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars

Research output: Contribution to journalArticlepeer-review

### Standard

LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars. / Gürkan, Gülay; Hardcastle, Martin; Best, Philip; Morabito, Leah; Prandoni, Isabella; Jarvis, Matt; Duncan, Ken; Rivera, Gabriela Calistro; Callingham, Joe; Cochrane, Rachel; Croston, Judith; Heald, George; Mingo, Beatriz; Mooney, Sean; Sabater, Jose; Röttgering, Huub; Shimwell, Timothy; Smith, Dan; Tasse, Cyril; Williams, Wendy.

In: Astronomy & Astrophysics, 10.10.2018.

Research output: Contribution to journalArticlepeer-review

### Harvard

Gürkan, G, Hardcastle, M, Best, P, Morabito, L, Prandoni, I, Jarvis, M, Duncan, K, Rivera, GC, 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

### APA

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

### Author

Gürkan, Gülay ; Hardcastle, Martin ; Best, Philip ; Morabito, Leah ; Prandoni, Isabella ; Jarvis, Matt ; Duncan, Ken ; Rivera, Gabriela Calistro ; Callingham, Joe ; Cochrane, Rachel ; Croston, Judith ; Heald, George ; Mingo, Beatriz ; Mooney, Sean ; Sabater, Jose ; Röttgering, Huub ; Shimwell, Timothy ; Smith, Dan ; Tasse, Cyril ; Williams, Wendy. / LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars. In: Astronomy & Astrophysics. 2018.

### Bibtex

@article{bf3d421ef5de41bbb192f91db8f3c11d,
title = "LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars",
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). ",
keywords = "astro-ph.GA",
author = "G{\"u}lay G{\"u}rkan and Martin Hardcastle and Philip Best and Leah Morabito and Isabella Prandoni and Matt Jarvis and Ken Duncan and Rivera, {Gabriela Calistro} and Joe Callingham and Rachel Cochrane and Judith Croston and George Heald and Beatriz Mingo and Sean Mooney and Jose Sabater and Huub R{\"o}ttgering and Timothy Shimwell and Dan Smith and Cyril Tasse and Wendy Williams",
note = "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. {\textcopyright} 2018 ESO. ",
year = "2018",
month = oct,
day = "10",
doi = "10.1051/0004-6361/201833892",
language = "English",
journal = "Astronomy & Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",

}

### RIS

TY - JOUR

T1 - LoTSS/HETDEX: Optical quasars I. Low-frequency radio properties of optically selected quasars

AU - Gürkan, Gülay

AU - Hardcastle, Martin

AU - Best, Philip

AU - Morabito, Leah

AU - Prandoni, Isabella

AU - Jarvis, Matt

AU - Duncan, Ken

AU - Rivera, Gabriela Calistro

AU - Callingham, Joe

AU - Cochrane, Rachel

AU - Croston, Judith

AU - Heald, George

AU - Mingo, Beatriz

AU - Mooney, Sean

AU - Sabater, Jose

AU - Röttgering, Huub

AU - Shimwell, Timothy

AU - Smith, Dan

AU - Tasse, Cyril

AU - Williams, Wendy

N1 - 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.

PY - 2018/10/10

Y1 - 2018/10/10

N2 - 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).

AB - 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).

KW - astro-ph.GA

U2 - 10.1051/0004-6361/201833892

DO - 10.1051/0004-6361/201833892

M3 - Article

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

ER -