LoTSS/HETDEX: Optical quasars

Gürkan, G.; Hardcastle, M. J.; Best, P. N.; Morabito, L. K.; Prandoni, I.; Jarvis, M. J.; Duncan, K. J.; Rivera, G. Calistro; Callingham, J. R.; Cochrane, R. K.; Croston, J. H.; Heald, G.; Mingo, B.; Mooney, S.; Sabater, J.; Röttgering, H. J. A.; Shimwell, T. W.; Smith, D. J. B.; Tasse, C.; Williams, W. L.

doi:10.1051/0004-6361/201833892

Cited by 61 publications

(74 citation statements)

References 101 publications

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“…The canonical FRI/II luminosity break is around L 150 ∼ 10 26 W Hz −1 (Fanaroff & Riley 1974;Ledlow & Owen 1996). In our sample a significant minority of FRIs lie above this luminosity (194 sources, or Gürkan et al 2019). Roughly 45 per cent of the luminous FRIs in our sample are indeed quasars with z > 0.8.…”

Section: Fri and Frii Radio Properties In Lotssmentioning

confidence: 60%

Revisiting the Fanaroff–Riley dichotomy and radio-galaxy morphology with the LOFAR Two-Metre Sky Survey (LoTSS)

Mingo

Croston

Hardcastle

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Abstract The relative positions of the high and low surface brightness regions of radio-loud active galaxies in the 3CR sample were found by Fanaroff and Riley to be correlated with their luminosity. We revisit this canonical relationship with a sample of 5805 extended radio-loud active galactic nuclei (AGN) from the LOFAR Two-Metre Sky Survey (LoTSS), compiling the most complete data set of radio-galaxy morphological information obtained to date. We demonstrate that, for this sample, radio luminosity does not reliably predict whether a source is edge-brightened (FRII) or centre-brightened (FRI). We highlight a large population of low-luminosity FRIIs, extending three orders of magnitude below the traditional FR break, and demonstrate that their host galaxies are on average systematically fainter than those of high-luminosity FRIIs and of FRIs matched in luminosity. This result supports the jet power/environment paradigm for the FR break: low-power jets may remain undisrupted and form hotspots in lower mass hosts. We also find substantial populations that appear physically distinct from the traditional FR classes, including candidate restarting sources and ‘hybrids’. We identify 459 bent-tailed sources, which we find to have a significantly higher SDSS cluster association fraction (at z < 0.4) than the general radio-galaxy population, similar to the results of previous work. The complexity of the LoTSS faint, extended radio sources not only demonstrates the need for caution in the automated classification and interpretation of extended sources in modern radio surveys, but also reveals the wealth of morphological information such surveys will provide and its value for advancing our physical understanding of radio-loud AGN.

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Section: Fri and Frii Radio Properties In Lotssmentioning

confidence: 60%

Revisiting the Fanaroff–Riley dichotomy and radio-galaxy morphology with the LOFAR Two-Metre Sky Survey (LoTSS)

Mingo

Croston

Hardcastle

et al. 2019

Monthly Notices of the Royal Astronomical Society

Self Cite

178

223

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“…Another study using a sample with S 1.4GHz ≥ 11.5 µJy applied spectral energy distribution fitting and led to similar conclusions: the peak of the radio LF is at z ∼ 2 (Ceraj et al 2018). The radio loudness dichotomy was addressed also at low radio frequencies (120 − 168 MHz, Gürkan et al 2019), concluding that low-power quasars are dominated by star formation.…”

Section: Introductionmentioning

confidence: 99%

Unveiling the weak radio quasar population at $z\ge 4$

Perger

Frey

Gabányi

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We applied image stacking on empty-field Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey maps centred on optically identified high-redshift quasars at z ≥ 4 to uncover the hidden µJy radio emission in these active galactic nuclei (AGN). The median stacking procedure for the full sample of 2229 optically identified AGN uncovered an unresolved point source with an integrated flux density of 52 µJy, with a signal-to-noise ratio ∼ 10. We co-added the individual image centre pixels to estimate the characteristic monochromatic radio power at 1.4 GHz considering various values for the radio spectral index, revealing a radio population with P 1.4GHz ∼ 10 24 W Hz −1 . Assuming that the entire radio emission originates from star-forming (SF) activity in the nuclear region of the host galaxy, we obtained an upper limit on the characteristic star formation rate, ∼ 4200 M ⊙ yr −1 . The angular resolution of FIRST images is insufficient to distinguish between the SF and AGN origin of radio emission at these redshifts. However, a comparison with properties of individual sources from the literature indicates that a mixed nature is likely. Future very long baseline interferometry radio observations and ultra-deep Square Kilometre Array surveys are expected to be sensitive enough to detect and resolve the central 1−10 kpc region in the host galaxies, and thus discriminate between SF and AGN related emission.

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“…Although the time evolution of some radio loud quasars may lead to radio quiet quasars, these constitute a minority among the overall AGN phenomenon in the model and therefore the radio loud/radio quiet dichotomy can be understood without appealing to time evolution (see Garofalo et al 2016, and Garofalo, Christian & Jones 2019, for time evolution as connected to the time dependent merger function). The fact that radio loudness is not a dichotomy but a continuous phenomenon (Gurkan et al 2019) can also be understood in terms of a range in black hole spin values spanning the full retrograde/prograde regime. A prediction of all this is that as observations explore narrower high mass ranges of halo and black hole mass, the clustering preference of RLQ versus RQQ should decrease.…”

Section: Discussionmentioning

confidence: 99%

Why Radio Quiet Quasars are Preferred over Radio Loud Quasars Regardless of Environment and Redshift

Garofalo

North

Belga

et al. 2020

ApJ

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Evidence has accumulated suggesting the clustering of radio loud quasars is greater than for radio quiet quasars. We interpret these results in a context in which the fraction of radio loud quasar formation is fRLQ ≤ fRQQ compared to that for radio quiet quasars for all environments and redshift. Because we assume that post-merger cold gas onto large black holes produces either a radio loud or a radio quiet quasar, we show that for largest black hole masses that live in largest dark matter halos, fRLQ approaches 0.5 from below but does not exceed it, such that in rich clusters the formation of a radio loud quasar tends to be equally likely to occur as a radio quiet quasar. In dark matter halos with smaller mass, by contrast, radio quiet quasars are more likely to form and the likelihood increases inversely with dark matter halo mass. As a result, averaging over a population of radio loud and radio quiet quasars will necessarily generate lower average black hole masses for the radio quiet subgroup. Hence, despite the fact that the formation of radio quiet quasars is preferred over radio loud quasars in any environment, at any mass scale, at any luminosity, or redshift, averaging over a range of radio loud quasars will give the appearance they are preferred in cluster environments over radio quiet quasars. We show how this also accounts for the order of magnitude difference in the total number of jetted active galaxies compared to non-jetted counterparts.I.

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LoTSS/HETDEX: Optical quasars

Cited by 61 publications

References 101 publications

Revisiting the Fanaroff–Riley dichotomy and radio-galaxy morphology with the LOFAR Two-Metre Sky Survey (LoTSS)

Revisiting the Fanaroff–Riley dichotomy and radio-galaxy morphology with the LOFAR Two-Metre Sky Survey (LoTSS)

Unveiling the weak radio quasar population at $z\ge 4$

Why Radio Quiet Quasars are Preferred over Radio Loud Quasars Regardless of Environment and Redshift

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