scholarly journals Simulations of the Polarized Sky for the SKA: How to Constrain Intracluster Magnetic Fields

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 133 ◽  
Author(s):  
Francesca Loi ◽  
Matteo Murgia ◽  
Federica Govoni ◽  
Valentina Vacca ◽  
Isabella Prandoni ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Galaxy Clusters ◽  
Thermal Noise ◽  
Radio Sources ◽  
Rotation Measure ◽  
Square Kilometer Array ◽  
Discrete Radio Sources ◽  
Simulated Images ◽  
Enormous Number ◽  
The Universe

The advent of the Square Kilometer Array (SKA) will have unprecedented impact on the study of magnetic fields in galaxy clusters. This instrument will be able to perform all-sky surveys in polarization, allowing us to build a rotation-measure (RM) grid based on an enormous number of sources. However, it is not always obvious how to extract correct information about the strength and the structure of magnetic fields from the RM grid. The simulations presented here help us to investigate this topic as they consist of full-Stokes idealized (because we did not add thermal noise) images of a pair of galaxy clusters between 950–1760 GHz, i.e., the SKA1-MID band 2. These images include not just cluster-embedded radio sources but also foreground and background discrete radio sources populating the simulated portion of the universe. To study the magnetic fields of the simulated galaxy clusters, we applied the RM synthesis technique on the simulated images and compared the “true” cluster RM values with those inferred from RM synthesis. The accuracy of our methodology is guarantee by the excellent agreement that we observed when we considered only the signal from the background radio sources. The presence of a Faraday screen, foreground, and cluster sources, introduces degeneracies and/or ambiguities that make the interpretation of the results more difficult.

scholarly journals Rotation measure synthesis applied to synthetic SKA images of galaxy clusters

2019 ◽  
Vol 490 (4) ◽  
pp. 4841-4857 ◽  
Author(s):  
F Loi ◽  
M Murgia ◽  
F Govoni ◽  
V Vacca ◽  
A Bonafede ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Galaxy Clusters ◽  
Thermal Noise ◽  
Radio Telescopes ◽  
Input Information ◽  
Synthesis Technique ◽  
Rotation Measure ◽  
Potential Impact ◽  
Simulation Input

ABSTRACT Future observations with next-generation radio telescopes will help us to understand the presence and evolution of magnetic fields in galaxy clusters through determination of the so-called rotation measure (RM). In this work, we applied the RM synthesis technique to synthetic first phase Square Kilometre Array mid frequency element (i.e. the SKA1-MID) radio images of a pair of merging galaxy clusters, measured between 950 and 1750 MHz with a resolution of 10 arcsec and thermal noise of 0.1μJy beam−1. The results of our RM synthesis analysis are compared with the simulation input parameters. We study two cases: one with radio haloes at the cluster centres and another without. We found that the information obtained with RM synthesis is in general agreement with the input information; however, some discrepancies are present. We characterize them in this work, with the final goal of determining the potential impact of SKA1-MID on the study of cluster magnetic fields.

scholarly journals Connecting magnetic fields from sub-galactic scale to clusters of galaxies and beyond with cosmological MHD simulations

2015 ◽  
Vol 11 (A29B) ◽  
pp. 699-699
Author(s):  
Klaus Dolag ◽  
Alexander M. Beck ◽  
Alexander Arth
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Heat Transport ◽  
Galaxy Clusters ◽  
Large Scale ◽  
High Redshift ◽  
Galactic Halos ◽  
Rotation Measure ◽  
The Magnetic Field ◽  
Good Agreement

AbstractUsing the MHD version of Gadget3 (Stasyszyn, Dolag & Beck 2013) and a model for the seeding of magnetic fields by supernovae (SN), we performed simulations of the evolution of the magnetic fields in galaxy clusters and study their effects on the heat transport within the intra cluster medium (ICM). This mechanism – where SN explosions during the assembly of galaxies provide magnetic seed fields – has been shown to reproduce the magnetic field in Milky Way-like galactic halos (Beck et al. 2013). The build up of the magnetic field at redshifts before z = 5 and the accordingly predicted rotation measure evolution are also in good agreement with current observations. Such magnetic fields present at high redshift are then transported out of the forming protogalaxies into the large-scale structure and pollute the ICM (in a similar fashion to metals transport). Here, complex velocity patterns, driven by the formation process of cosmic structures are further amplifying and distributing the magnetic fields. In galaxy clusters, the magnetic fields therefore get amplified to the observed μG level and produce the observed amplitude of rotation measures of several hundreds of rad/m2. We also demonstrate that heat conduction in such turbulent fields on average is equivalent to a suppression factor around 1/20th of the classical Spitzer value and in contrast to classical, isotropic heat transport leads to temperature structures within the ICM compatible with observations (Arth et al. 2014).

scholarly journals Developed turbulence and nonlinear amplification of magnetic fields in laboratory and astrophysical plasmas

2015 ◽  
Vol 112 (27) ◽  
pp. 8211-8215 ◽  
Author(s):  
Jena Meinecke ◽  
Petros Tzeferacos ◽  
Anthony Bell ◽  
Robert Bingham ◽  
Robert Clarke ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Galaxy Clusters ◽  
Density Fluctuations ◽  
Line Broadening ◽  
Astrophysical Plasmas ◽  
Developed Turbulence ◽  
Visible Matter ◽  
Merger Event ◽  
The Universe ◽  
The Magnetic Field

The visible matter in the universe is turbulent and magnetized. Turbulence in galaxy clusters is produced by mergers and by jets of the central galaxies and believed responsible for the amplification of magnetic fields. We report on experiments looking at the collision of two laser-produced plasma clouds, mimicking, in the laboratory, a cluster merger event. By measuring the spectrum of the density fluctuations, we infer developed, Kolmogorov-like turbulence. From spectral line broadening, we estimate a level of turbulence consistent with turbulent heating balancing radiative cooling, as it likely does in galaxy clusters. We show that the magnetic field is amplified by turbulent motions, reaching a nonlinear regime that is a precursor to turbulent dynamo. Thus, our experiment provides a promising platform for understanding the structure of turbulence and the amplification of magnetic fields in the universe.

scholarly journals Relativistic plasma and ICM/radio source interaction

2010 ◽  
Vol 6 (S274) ◽  
pp. 340-347 ◽  
Author(s):  
Luigina Feretti ◽  
Gabriele Giovannini ◽  
Federica Govoni ◽  
Matteo Murgia
Keyword(s):  
Magnetic Fields ◽  
Radio Source ◽  
Large Scale ◽  
Large Scale Structure ◽  
Radio Sources ◽  
Relativistic Electrons ◽  
Coma Cluster ◽  
Cluster Of Galaxies ◽  
Formation And Evolution ◽  
The Universe

AbstractThe first detection of a diffuse radio source in a cluster of galaxies, dates back to the 1959 (Coma Cluster, Large et al. 1959). Since then, synchrotron radiating radio sources have been found in several clusters, and represent an important cluster component which is linked to the thermal gas. Such sources indicate the existence of large scale magnetic fields and of a population of relativistic electrons in the cluster volume. The observational results provide evidence that these phenomena are related to turbulence and shock-structures in the intergalactic medium, thus playing a major role in the evolution of the large scale structure in the Universe. The interaction between radio sources and cluster gas is well established in particular at the center of cooling core clusters, where feedback from AGN is a necessary ingredient to adequately describe the formation and evolution of galaxies and host clusters.

scholarly journals A SUMMARY OF RADIO PULSAR POLARIZATION

2013 ◽  
Vol 23 ◽  
pp. 174-178
Author(s):  
C. ZHU ◽  
W. M. YAN ◽  
N. WANG
Keyword(s):  
Interstellar Medium ◽  
Radio Pulsar ◽  
Radio Sources ◽  
Radio Pulsars ◽  
Emission Process ◽  
Polarization Measurements ◽  
Rotation Measure ◽  
The Universe

Pulsars are one of the most polarized radio sources in the universe. Polarization measurements of pulsars provide us a lot of information, not only about the emission process itself, but also about the interstellar medium. This article describes the polarization properties of radio pulsars in general and discusses the observed rotation measure variations with time in pulsars.

scholarly journals RM due to magnetic fields in the cosmic web and SKA observations

2012 ◽  
Vol 10 (H16) ◽  
pp. 407-407 ◽  
Author(s):  
Takuya Akahori ◽  
Dongsu Ryu
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Rotation Measure ◽  
Square Kilometer Array ◽  
Intergalactic Magnetic Field

AbstractWe estimated that rotation measure (RM) due to the intergalactic magnetic field (IGMF) in the cosmic web is ~ 1–10 rad m−2. The RMs could be tested with the Square Kilometer Array (SKA) and SKA pathfinders.

scholarly journals Constraining magnetic fields in galaxy clusters

2018 ◽  
Vol 14 (A30) ◽  
pp. 299-302
Author(s):  
Annalisa Bonafede ◽  
Chiara Stuardi ◽  
Federica Savini ◽  
Franco Vazza ◽  
Marcus Brüggen
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Magnetic Fields ◽  
Galaxy Clusters ◽  
Faraday Rotation ◽  
Small Scale ◽  
Radio Sources ◽  
Synchrotron Emission ◽  
Combined Approach ◽  
The Magnetic Field

AbstractMagnetic fields originate small-scale instabilities in the plasma of the intra-cluster medium, and may have a key role to understand particle acceleration mechanisms. Recent observations at low radio frequencies have revealed that synchrotron emission from galaxy clusters is more various and complicated than previously thought, and new types of radio sources have been observed. In the last decade, big steps forward have been done to constrain the magnetic field properties in clusters thanks to a combined approach of polarisation observations and numerical simulations that aim to reproduce Faraday Rotation measures of sources observed through the intra-cluster medium. In this contribution, I will review the results on magnetic fields reached in the last years, and I will discuss the assumptions that have been done so far in light of new results obtained from cosmological simulations. I will also discuss how the next generation of radio instruments, as the SKA, will help improving our knowledge of the magnetic field in the intra-cluster medium.

scholarly journals The Magnetic Fields of the Universe and Their Origin

2000 ◽  
Vol 195 ◽  
pp. 255-264 ◽  
Author(s):  
S. A. Colgate ◽  
H. Li
Keyword(s):  
Magnetic Fields ◽  
Accretion Disk ◽  
Free Field ◽  
Back Reaction ◽  
Winding Number ◽  
Massive Black Hole ◽  
Rotation Measure ◽  
Disk Dynamo ◽  
The Universe ◽  
Force Free Field

Recent rotation-measure observations of a dozen or so galaxyclusters have revealed a surprisingly large number of magnetic fields whose estimated energy and flux are, on average, ~ 1058 ergs and ~ 1041 G cm2, respectively. These quantities are so much larger than any coherent sums of individual galaxies within the cluster that an efficient galactic dynamo is required. We associate these fields with single AGNs within the cluster and, therefore, with all galaxies during their AGN phase. Only the central, massive black hole (BH) has the necessary binding energy, ~ 1061 ergs. Only the accretion disk during the BH formation has the winding number, ~ 1011 turns, necessary to make the gain and magnetic flux. We present a model of a BH accretion-disk dynamo that might create these magnetic fields, where the helicity of the α-Ω dynamo is driven by star-disk collisions. The back reaction of the saturated dynamo forms a force-free field helix that carries the energy and flux of the dynamo and redistributes them within the clusters.

scholarly journals Magnetic Fields in Galaxy Clusters and in the Large-Scale Structure of the Universe

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 142 ◽  
Author(s):  
Valentina Vacca ◽  
Matteo Murgia ◽  
Federica Govoni ◽  
Torsten Enßlin ◽  
Niels Oppermann ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Quality Data ◽  
High Quality Data ◽  
History Of ◽  
The Universe ◽  
Detailed Picture

The formation and history of cosmic magnetism is still widely unknown. Significant progress can be made through the study of magnetic fields properties in the large-scale structure of the Universe: galaxy clusters, filaments, and voids of the cosmic web. A powerful tool to study magnetization of these environments is represented by radio observations of diffuse synchrotron sources and background or embedded radio galaxies. To draw a detailed picture of cosmic magnetism, high-quality data of these sources need to be used in conjunction with sophisticated tools of analysis.

scholarly journals Simulations and observational tests of primordial magnetic fields from Cosmic Microwave Background constraintsok

2020 ◽  
Vol 500 (4) ◽  
pp. 5350-5368
Author(s):  
F Vazza ◽  
D Paoletti ◽  
S Banfi ◽  
F Finelli ◽  
C Gheller ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Cosmic Microwave Background ◽  
Galaxy Clusters ◽  
Faraday Rotation ◽  
Gravitational Effect ◽  
High Energy ◽  
Microwave Background ◽  
High Energy Cosmic Rays ◽  
Rotation Measure ◽  
Primordial Magnetic Fields

ABSTRACT We present the first cosmological simulations of primordial magnetic fields derived from the constraints by the Cosmic Microwave Background observations, based on the fields’ gravitational effect on cosmological perturbations. We evolved different primordial magnetic field models with the enzo code and compared their observable signatures (and relative differences) in galaxy clusters, filaments, and voids. The differences in synchrotron radio powers and Faraday rotation measure from galaxy clusters are generally too small to be detected, whereas differences present in filaments will be testable with the higher sensitivity of the Square Kilometre Array. However, several statistical full-sky analyses, such as the cross-correlation between galaxies and diffuse synchrotron power, the Faraday rotation structure functions from background radio galaxies, or the analysis of arrival direction of ultra-high-energy cosmic rays, can already be used to constrain these primordial field models.

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