Wide-field imaging and polarimetry for the biggest and brightest in the 20-GHz southern sky

Burke-Spolaor, S.; Ekers, R. D.; Massardi, M.; Murphy, Tara; Partridge, B.; Ricci, R.; Sadler, E. M.

doi:10.1111/j.1365-2966.2009.14556.x

Cited by 21 publications

(42 citation statements)

References 75 publications

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“…Moreover, those authors noted a minimum of emission along the jets axes, reminding a double-double morphology. A similar morphology is seen in the ATCA image at 20 GHz presented by Burke-Spolaor et al (2009), where a further minimum of emission, this time between the core and the supposed inner sets of lobes, is evident. Moreover, the bottle-necked morphology of the external sets of lobes ( Fig.…”

Section: Images From Surveys and The Literaturesupporting

confidence: 78%

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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Section: Images From Surveys and The Literaturesupporting

confidence: 78%

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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“…• , and hence the jet luminosity, roughly, L j πR 2 cΓ (2001), Fey et al (2004) and Burke-Spolaor et al (2009). The ASCA measurements of the lobes' and core spectra within the range 0.7−10 keV, as discussed in Tashiro et al (1998), are denoted by red and blue bow ties, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…A substantial amount of flux is lost, since the shortest baseline between antennas (∼20 m for mosaicked images from the ATCA) is too large to recover the emission on the largest spatial scales. The entire source has also been imaged at 20 GHz (Burke-Spolaor et al 2009). Again, the integrated fluxes cannot be used in our SED modeling due to the missing short spacings, although the results provide an accurate representation of the core, jet, and hotspot structures.…”

Section: Lobesmentioning

confidence: 99%

Fermi-LAT andSuzakuobservations of the radio galaxy Centaurus B

Katsuta

Tanaka

Stawarz

et al. 2013

A&A

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Centaurus B is a nearby radio galaxy positioned in the southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months of accumulated Fermi-LAT data of the γ-ray counterpart of the source initially reported in the 2nd Fermi-LAT catalog, and of newly acquired Suzaku X-ray data. We confirm its detection at GeV photon energies and analyze the extension and variability of the γ-ray source in the LAT dataset, in which it appears as a steady γ-ray emitter. The X-ray core of Centaurus B is detected as a bright source of a continuum radiation. We do not detect, however, any diffuse X-ray emission from the known radio lobes, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. Two scenarios that connect the X-ray and γ-ray properties are considered. In the first one, we assume that the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. In this case, modeling the inverse-Compton emission shows that the observed γ-ray flux of the source may in principle be produced within the lobes. This association would imply that efficient in-situ acceleration of the radiating electrons is occurring and that the lobes are dominated by the pressure from the relativistic particles. In the second scenario, with the diffuse X-ray emission well below the Suzaku upper limits, the lobes in the system are instead dominated by the magnetic pressure. In this case, the observed γ-ray flux is not likely to be produced within the lobes, but instead within the nuclear parts of the jet. By means of synchrotron self-Compton modeling, we show that this possibility could be consistent with the broad-band data collected for the unresolved core of Centaurus B, including the newly derived Suzaku spectrum.

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“…The 30‐m spacing used for the blind survey underestimates the amplitude by 50 per cent and the survey is increasingly incomplete for more extended sources. Integrated flux densities at 20GHz have been obtained for nine very extended extragalactic sources (Burke‐Spolaor et al 2009). The flux densities determined for the seven sources included in AT20G survey were added to the final catalogue.…”

Section: Sample Definition and Propertiesmentioning

confidence: 99%

The Australia Telescope 20 GHz (AT20G) Survey: analysis of the extragalactic source sample

Massardi

Ekers

Murphy

et al. 2011

Monthly Notices of the Royal Astronomical Society

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The Australia Telescope 20 GHz (AT20G) survey is a blind survey of the whole Southern sky at 20 GHz with follow‐up observations at 4.8, 8.6 and 20 GHz carried out with the Australia Telescope Compact Array (ATCA) from 2004 to 2008. In this paper we present an analysis of radio spectral properties in total intensity and polarization, sizes, optical identifications and redshifts of the sample of the 5808 extragalactic sources in the survey catalogue of confirmed sources over 6.1 sr in the Southern sky (i.e. the whole Southern sky excluding the strip at Galactic latitude |b| < ). The sample has a flux density limit of 40 mJy. Completeness has been measured as a function of scan region and flux density. Averaging over the whole survey area the follow‐up survey is 78 per cent complete above 50 mJy and 93 per cent complete above 100 mJy. 3332 sources with declination δ < −15° have good quality almost simultaneous observations at 4.8, 8.6 and 20 GHz. The spectral analysis shows that the sample is dominated by flat‐spectrum sources, with 69 per cent having spectral index α208.6 > − 0.5 (S∝να). The fraction of flat‐spectrum sources decreases from 81 per cent for S20 GHz > 500 mJy to 60 per cent for S20 GHz < 100 mJy. There is also a clear spectral steepening at higher frequencies with the median α decreasing from −0.16 between 4.8 and 8.6 GHz to −0.28 between 8.6 and 20 GHz. Simultaneous observations in polarization are available for all the sources at all the frequencies. 768 sources have a good‐quality detection of polarized flux density at 20 GHz; 467 of them were also detected in polarization at 4.8 and/or at 8.6 GHz so that it has been possible to compare the spectral behaviour in total intensity and polarization. We have found that the polarized fraction increases slightly with frequency and decreases with flux density. The spectral indices in total intensity and in polarization are, on average, close to each other, but we also found several sources for which the spectral shape of the polarized emission is substantially different from the spectral shape in total intensity. The correlation between the spectral indices in total intensity and in polarization is weaker for flat‐spectrum sources. Cross‐matches and comparisons have been made with other catalogues at lower radio frequencies, and in the optical, X‐ray and γ‐ray bands. Redshift estimates are available for 825 sources.

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Wide-field imaging and polarimetry for the biggest and brightest in the 20-GHz southern sky

Cited by 21 publications

References 75 publications

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

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

Fermi-LAT andSuzakuobservations of the radio galaxy Centaurus B

The Australia Telescope 20 GHz (AT20G) Survey: analysis of the extragalactic source sample

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