Extragalactic Peaked-spectrum Radio Sources at Low Frequencies

Callingham, J. R.; Ekers, R. D.; Gaensler, B. M.; Line, J.; Hurley‐Walker, N.; Sadler, E. M.; Tingay, S. J.; Hancock, P. J.; Bell, M. E.; Dwarakanath, K. S.; For, Bi-Qing; Franzen, T. M. O.; Hindson, L.; Johnston‐Hollitt, M.; Kapińska, A. D.; Lenc, E.; McKinley, B.; Morgan, John S.; Offringa, A. R.; Procopio, P.; Staveley‐Smith, L.; Wayth, R. B.; Wu, Chen; Zheng, Qian

doi:10.3847/1538-4357/836/2/174

Cited by 151 publications

(233 citation statements)

References 197 publications

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“…These redshifted components (1 to 4) may be gas clouds in-falling toward the AGN, as seen in van Gorkom et al (1989). We note that PKS 1829−718 was identified as a GPS source in Callingham et al (2017) with a peak frequency near 1 GHz, which typically indicates a linear extent of <1 kpc.…”

Section: Pks 1829−718mentioning

confidence: 86%

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An ASKAP survey for H i absorption towards dust-obscured quasars

Glowacki

Allison

Moss

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Obscuration of quasars by accreted gas and dust, or dusty intervening galaxies, can cause active galactic nuclei (AGN) to be missed in optically-selected surveys. Radio observations can overcome this dust bias. In particular, radio surveys searching for Hi absorption inform us on how the AGN can impact on the cold neutral gas medium within the host galaxy, or the population of intervening galaxies through the observed line of sight gas kinematics. We present the results of a Hi absorption line survey at 0.4 < z < 1 towards 34 obscured quasars with the Australian SKA Pathfinder (ASKAP) commissioning array. We detect three Hi absorption lines, with one of these systems previously unknown. Through optical follow-up for two sources, we find that in all detections the Hi gas is associated with the AGN, and hence that these AGN are obscured by material within their host galaxies. Most of our sample are compact, and in addition, are either gigahertz peaked spectrum (GPS), or steep spectrum (CSS) sources, both thought to represent young or recently re-triggered radio AGN. The radio spectral energy distribution classifications for our sample agree with galaxy evolution models in which the obscured AGN has only recently become active. Our associated Hi detection rate for GPS and compact SS sources matches those of other surveys towards such sources. We also find shallow and asymmetric Hi absorption features, which agrees with previous findings that the cold neutral medium in compact radio galaxies is typically kinematically disturbed by the AGN.

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Section: Pks 1829−718mentioning

confidence: 86%

“…A generic curved model fit (black) and a power-law fit is made for each SED as per the model fitting code described in Callingham et al (2015). All three sources here are identified as peak-spectrum sources by Callingham et al (2017) and so only have curved model fits present.…”

Section: Hunstead 2006bmentioning

confidence: 99%

An ASKAP survey for H i absorption towards dust-obscured quasars

Glowacki

Allison

Moss

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The dashed lines show the evolutionary curves of the frequency peak for ν int = 0.5 and 10 GHz; the solid line corresponds to the minimum value of the frequency ν int at a certain redshift. The black stars show the data for the comparison sample based on objects of the GLEAM low-frequency survey [41].…”

Section: Discussionmentioning

confidence: 99%

Multifrequency Study of GHz-peaked Spectrum Sources

et al. 2019

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Gigahertz-Peaked spectrum (GPS) sources are compact active galactic nuclei, presumably young precursors of bright radio sources. The study of GPS radio properties provides information about the features of synchrotron radiation in extragalactic sources. Also in applied research GPS sources are useful as compact stationary radio sources in the sky for astrometric purposes. This paper presents the results of a multifrequency GPS study based on quasi-simultaneous measurements with the RATAN-600 radio telescope during the 2006-2017. The catalog containing spectral flux densities measured at six frequencies (1.1, 2.3, 4.8, 7.7/8.2, 11.2, and 21.7 GHz) have been obtained. In addition, for the analysis of radio spectra, data from the following low-frequency surveys have been used: GLEAM (GaLactic and Extragalactic All-sky Murchison widefield array survey) and TGSS (Tata institute for fundamental research GMRT Sky Survey) and high-frequency measurements from Planck survey. A total number of 164 GPS and candidates to GPS have been identified (17 of them are new discoveries), which makes up a small fraction of GPS in the initial sample of bright AGNs, about 2%. The physical properties and formation conditions of synchrotron radiation is found to be quite different in GPS of different AGN types. The deficit of distant GPS (z > 2) with low maximum frequencies (less than 1 GHz) is confirmed. The existing "size -peak frequency" anticorrelation is continuous. The continuum radio spectra are found to become statistically steeper with increasing redshift.

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“…Further observations in the optical and X-ray band indicated a high flux variability (∼60% in 7 years), with variable broad H α emission and a broad [OIII] component, suggesting the presence of an outflow (Hernández-García et al 2018). Recently, Callingham et al (2017) presented this source as restarted, finding it to have a convex radio spectrum in the frequency range from MHz to GHz. The GMRT image at 150 MHz presented here confirms the GRG nature of this source, and shows a lack of emission between the lobes and the core region compatible with the change of jet axis proposed by Hernández-García et al (2017).…”

Section: Gmrt Imagesmentioning

confidence: 97%

Hard X-ray selected giant radio galaxies – II. Morphological evidence of restarted radio activity

Bruni

Panessa

Bassani³

et al. 2020

Monthly Notices of the Royal Astronomical Society

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About 6% of Radio Galaxies (RG) can reach linear sizes larger than 0.7 Mpc, and are then classified as Giant Radio Galaxies (GRG). The conditions that make possible the formation of such big structures is still not clear -either core accretion properties or environmental factors. Recent studies have shown that GRG can be up to four times more abundant in hard X-ray selected (i.e. from INTEGRAL/IBIS and Swift/BAT at >20 keV) RG samples. Moreover, a high fraction of young radio sources found in their cores suggests a recently restarted activity, as suggested from the discrepancy between the measured jet and lobes power, with respect to the one expected from core X-ray luminosity. Here we present a radio morphological study of a sample of 15 hard X-ray selected GRG, discussing low-frequency images from our GMRT campaign complemented with others from the literature: among them, 7/15 show evidence of restarted radio activity either in the form of double-double/X-shaped morphology, or as a cocoon emission embedding more recent jets. This, together with the objects from this sample already found hosting a young radio source in their core, suggests that at least 13 over 15 of these hard X-ray selected GRG show features which are consistent with the possibility of restarted radio activity.

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Extragalactic Peaked-spectrum Radio Sources at Low Frequencies

Cited by 151 publications

References 197 publications

An ASKAP survey for H i absorption towards dust-obscured quasars

An ASKAP survey for H i absorption towards dust-obscured quasars

Multifrequency Study of GHz-peaked Spectrum Sources

Hard X-ray selected giant radio galaxies – II. Morphological evidence of restarted radio activity

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