Unexpected circular radio objects at high Galactic latitude

Norris, R. P.; Intema, H. T.; Kapińska, A. D.; Koribalski, B. S.; Lenc, E.; Rudnick, Lawrence; Alsaberi, R. Z. E.; Anderson, Craig S.; Anderson, G. E.; Crawford, E. J.; Crocker, Roland M.; English, Jayanne; Filipović, Miroslav; Galvin, T. J.; Hopkins, A. M.; Hurley‐Walker, N.; Inoue, Susumu; Luken, Kieran J.; Macgregor, Peter J.; Manojlović, P.; Marvil, J.; O’Brien, Andrew; Park, Laurence A; Raja, Wasim; Shobhana, Devika; Venturi, T.; Collier, Jordan D.; Hale, C. L.; Hotan, A. W.; Moss, V. A.; Whiting, M. T.

doi:10.1017/pasa.2020.52

Cited by 45 publications

(80 citation statements)

References 75 publications

(107 reference statements)

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“…It has been predicted that, because EMU would observe a previously inaccessible part of observational parameter space, it would probably make unexpected discoveries (Norris 2017b). Nevertheless, we were surprised to find an apparently new class of object appearing in the EMU-PS, consisting of circles of radio emission, typically one arcmin across, with no optical or infrared counterpart (Norris et al 2021). The first of these ORCs to be identified is shown in Figure 25, and another example is shown in Figure 17.…”

Section: Odd Radio Circlesmentioning

confidence: 98%

“…Several ORCs have a galaxy at the centre, typically at a redshift of ∼0.3 in the currently known examples. Potential explanations are that these central galaxies may be the origins of spherical shock (Norris et al 2021). It has no optical counterpart to the diffuse ring, or to other diffuse structure, but has a galaxy at its centre which may be the origin of the ring.…”

Section: Odd Radio Circlesmentioning

confidence: 99%

“…It has no optical counterpart to the diffuse ring, or to other diffuse structure, but has a galaxy at its centre which may be the origin of the ring. The image is based on EMU-PS data at native resolution but enhanced to show faint features as described in Norris et al (2021), particularly the internal structure or "spokes" of the ORC. Radio data are shown in green, and DES optical data are shown in turquoise, magenta, yellow and red, and mainly appear in this image as white.…”

Section: Odd Radio Circlesmentioning

confidence: 99%

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The Evolutionary Map of the Universe pilot survey

Norris

Marvil

Collier

et al. 2021

Publ. Astron. Soc. Aust.

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100

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We present the data and initial results from the first pilot survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The survey covers $270 \,\mathrm{deg}^2$ of an area covered by the Dark Energy Survey, reaching a depth of 25–30 $\mu\mathrm{Jy\ beam}^{-1}$ rms at a spatial resolution of $\sim$ 11–18 arcsec, resulting in a catalogue of $\sim$ 220 000 sources, of which $\sim$ 180 000 are single-component sources. Here we present the catalogue of single-component sources, together with (where available) optical and infrared cross-identifications, classifications, and redshifts. This survey explores a new region of parameter space compared to previous surveys. Specifically, the EMU Pilot Survey has a high density of sources, and also a high sensitivity to low surface brightness emission. These properties result in the detection of types of sources that were rarely seen in or absent from previous surveys. We present some of these new results here.

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Section: Odd Radio Circlesmentioning

confidence: 98%

Section: Odd Radio Circlesmentioning

confidence: 99%

Section: Odd Radio Circlesmentioning

confidence: 99%

See 1 more Smart Citation

The Evolutionary Map of the Universe pilot survey

Norris

Marvil

Collier

et al. 2021

Publ. Astron. Soc. Aust.

Self Cite

100

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“…The morphology of the φ peak,res enhancement is revealed in Figure 8, where we interpolate (using the nearest neighbour method) and plot φ 2 peak,res as a function of position. Contours showing the observable extent of the X-ray-emitting ICM as seen by Chandra (Scharf et al 2005) and ROSAT (Jones et al 1997) are overlaid, as are contours for the radio galaxy Fornax A (see Norris et al 2021). We note that the Chandra and ROSAT X-ray maps are smoothed to 2.5 and 3 arcminutes, respectively, to reveal the faint diffuse emission.…”

Section: Spatial Morphology Of the Faraday Depth Enhancementsmentioning

confidence: 99%

Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

Anderson

Heald

Eilek

et al. 2021

Publ. Astron. Soc. Aust.

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We present the first Faraday rotation measure (RM) grid study of an individual low-mass cluster—the Fornax cluster—which is presently undergoing a series of mergers. Exploiting commissioning data for the POlarisation Sky Survey of the Universe’s Magnetism (POSSUM) covering a ${\sim}34$ square degree sky area using the Australian Square Kilometre Array Pathfinder (ASKAP), we achieve an RM grid density of ${\sim}25$ RMs per square degree from a 280-MHz band centred at 887 MHz, which is similar to expectations for forthcoming GHz-frequency ${\sim}3\pi$ -steradian sky surveys. These data allow us to probe the extended magnetoionic structure of the cluster and its surroundings in unprecedented detail. We find that the scatter in the Faraday RM of confirmed background sources is increased by $16.8\pm2.4$ rad m−2 within 1 $^\circ$ (360 kpc) projected distance to the cluster centre, which is 2–4 times larger than the spatial extent of the presently detectable X-ray-emitting intracluster medium (ICM). The mass of the Faraday-active plasma is larger than that of the X-ray-emitting ICM and exists in a density regime that broadly matches expectations for moderately dense components of the Warm-Hot Intergalactic Medium. We argue that forthcoming RM grids from both targeted and survey observations may be a singular probe of cosmic plasma in this regime. The morphology of the global Faraday depth enhancement is not uniform and isotropic but rather exhibits the classic morphology of an astrophysical bow shock on the southwest side of the main Fornax cluster, and an extended, swept-back wake on the northeastern side. Our favoured explanation for these phenomena is an ongoing merger between the main cluster and a subcluster to the southwest. The shock’s Mach angle and stand-off distance lead to a self-consistent transonic merger speed with Mach 1.06. The region hosting the Faraday depth enhancement also appears to show a decrement in both total and polarised radio emission compared to the broader field. We evaluate cosmic variance and free-free absorption by a pervasive cold dense gas surrounding NGC 1399 as possible causes but find both explanations unsatisfactory, warranting further observations. Generally, our study illustrates the scientific returns that can be expected from all-sky grids of discrete sources generated by forthcoming all-sky radio surveys.

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“…Here, we see the two most promising possibilities. The first possibility relates to recently observed unexpected circular radio objects [31] and the possible role of torus-shaped wormholes in their origin [32]. The second relates to gravitational wave Astronomy.…”

Section: Introductionmentioning

confidence: 99%

Possible Effects of the Fractal Distribution of Relic Wormholes

2021

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We discuss the possibility that the distribution of relic wormholes may possess fractal properties. Relic wormholes and their fractal distributions are predicted in a natural way by lattice quantum gravity models. This provides a new approach to some long standing problems. That is the nature of dark matter phenomena, the origin of Faber-Jackson and Tully-Fisher relations and the observed deficit of baryons. We derive corrections to the Newton’s potential caused by the presence of relic wormholes and show that the analysis of dark matter distribution in galaxies allows us to fix the parameters of the fractal distribution of wormholes.

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Unexpected circular radio objects at high Galactic latitude

Cited by 45 publications

References 75 publications

The Evolutionary Map of the Universe pilot survey

The Evolutionary Map of the Universe pilot survey

Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

Possible Effects of the Fractal Distribution of Relic Wormholes

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