Synchrotron Emission on the Largest Scales: Radio Detection of the Cosmic-Web

Brown, Shea

doi:10.1007/s12036-011-9114-4

Cited by 33 publications

(47 citation statements)

References 38 publications

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“…Despite of a few claims of possible detections Farnsworth et al, 2013), the observation of large-scale shocks along filaments remains a challenge (e.g. Brown, 2011). In recent work, we have looked at the potential of existing and future surveys to detect the cosmic web in emission at radio wavelengths.…”

Section: Synchrotron Radio Emission From Shock-accelerated Electrons mentioning

confidence: 99%

“…However, only SKA-LOW should have the sensitivity on sufficiently large scales to perform this test, while in the case of SKA-MID the stacked emission will be below the detection limit in both cases. In addition to stacking clusters or filaments, there may be other ways to extract signals from the cosmic web (Brown, 2011;. For example, recent statistical studies based on the cross-correlation between radio surveys and galaxy surveys have derived upper limits on the magnetization of filaments of the order of ≤ 0.1µG , based on the absence of a strong correlation between synchrotron emission and the underlying galaxy distribution Brown et al, 2017).…”

Section: Synchrotron Radio Emission From Shock-accelerated Electrons mentioning

confidence: 99%

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Simulations of extragalactic magnetic fields and of their observables

Vazza

Brüggen

Gheller³

et al. 2017

Class. Quantum Grav.

131

228

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Abstract. The origin of extragalactic magnetic fields is still poorly understood. Based on a dedicated suite of cosmological magneto-hydrodynamical simulations with the ENZO code we have performed a survey of different models that may have caused present-day magnetic fields in galaxies and galaxy clusters. The outcomes of these models differ in cluster outskirts, filaments, sheets and voids and we use these simulations to find observational signatures of magnetogenesis. With these simulations, we predict the signal of extragalactic magnetic fields in radio observations of synchrotron emission from the cosmic web, in Faraday Rotation, in the propagation of Ultra High Energy Cosmic Rays, in the polarized signal from Fast Radio Bursts at cosmological distance and in spectra of distant blazars. In general, primordial scenarios in which present-day magnetic fields originate from the amplification of weak (≤ nG) uniform seed fields result more homogeneous and relatively easier to observe magnetic fields than than astrophysical scenarios, in which present-day fields are the product of feedback processes triggered by stars and active galaxies. In the near future the best evidence for the origin of cosmic magnetic fields will most likely come from a combination of synchrotron emission and Faraday Rotation observed at the periphery of large-scale structures.

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Section: Synchrotron Radio Emission From Shock-accelerated Electrons mentioning

confidence: 99%

Section: Synchrotron Radio Emission From Shock-accelerated Electrons mentioning

confidence: 99%

Simulations of extragalactic magnetic fields and of their observables

Vazza

Brüggen

Gheller³

et al. 2017

Class. Quantum Grav.

131

228

View full text Add to dashboard Cite

show abstract

“…For example, the Evolutionary Map of the Universe (Norris et al 2011) survey with the Australian Square Kilometre Array Pathfinder (ASKAP), will have an RMS noise on the order of 0.1 µJy/arcsec 2 , and could potentially reach the above limit directly so long as the interferometric nature of ASKAP does not filter out the diffuse emission (Brown 2011). Given the optimistic value of Xp assumed in this work, and the distance between our upper limit and the simulation magnetic field in Fig.…”

Section: Future Direct Detectionmentioning

confidence: 99%

Limiting magnetic fields in the cosmic web with diffuse radio emission

Brown

Vernstrom

Carretti

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We set limits on the presence of the synchrotron cosmic web through the crosscorrelation of the 2.3 GHz S-PASS survey with a model of the local cosmic web derived from constrained magnetohydrodynamic (MHD) simulations. The MHD simulation assumes cosmologically seeded magnetic fields amplified during large-scale structure formation, and a population of relativistic electrons/positrons from proton-proton collisions within the intergalactic medium. We set a model-dependent 3σ upper limit on the synchrotron surface brightness of 0.16 mJy arcmin −2 at 2.3 GHz in filaments. Extrapolating from magnetic field maps created from the simulation, we infer an upper limit (density-weighted) magnetic field of 0.03 (0.13) µG in filaments at the current epoch, and a limit on the primordial magnetic field (PMF) of B P M F <1.0 nG.

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“…The imaging step with the AW imager after the self-calibration results in a slightly higher noise level of ∼0.45 mJy beam −1 and a slightly higher dynamic range ∼5800. The resulting maps are confusion dominated toward its centre; indeed at 160 MHz and with a beam A72, page 4 of 13 M. Iacobelli et al: The first diffuse Galactic foreground detection with LOFAR size of about 1 , the expected confusion noise level is about 1 mJy beam −1 (Brown 2011).…”

Section: Continuum Emission Mapsmentioning

confidence: 99%

Studying Galactic interstellar turbulence through fluctuations in synchrotron emission

Iacobelli

Haverkorn

Orrù

et al. 2013

A&A

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Aims. The characteristic outer scale of turbulence (i.e. the scale at which the dominant source of turbulence injects energy to the interstellar medium) and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters. Methods. We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l, b) ∼ (137.0 • , +7.0 • ) at 80 × 70 resolution in the range [146, 174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations. Results. We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum displays a power law behaviour for scales between 100 and 8 arcmin with a slope α = −1.84 ± 0.19. We find an upper limit of ∼20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region, which is in agreement with previous estimates in literature. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes. Conclusions. We present the first LOFAR detection and imaging of the Galactic diffuse synchrotron emission around 160 MHz from the highly polarized Fan region. The power spectrum of the foreground synchrotron fluctuations is approximately a power law with a slope α ≈ −1.84 up to angular multipoles of 1300, corresponding to an angular scale of ∼8 arcmin. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of turbulence (L out ) of the Galactic synchrotron foreground, finding a range of plausible values of 10−20 pc. Then, we use this information to deduce lower limits of the ratio of ordered to random magnetic field strength. These are found to be 0.3, 0.3, and 0.5 for the LOFAR, WSRT and GMRT fields considered respectively. Both these constraints are in agreement with previous estimates.

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Synchrotron Emission on the Largest Scales: Radio Detection of the Cosmic-Web

Cited by 33 publications

References 38 publications

Simulations of extragalactic magnetic fields and of their observables

Simulations of extragalactic magnetic fields and of their observables

Limiting magnetic fields in the cosmic web with diffuse radio emission

Studying Galactic interstellar turbulence through fluctuations in synchrotron emission

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