A Faraday rotation search for magnetic fields in quasar damped LY alpha absorption systems

Oren, A. L.; Wolfe, Arthur M.

doi:10.1086/175726

Cited by 92 publications

(93 citation statements)

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“…Kronberg & Perry (1982) found an increased variance of the Faraday depth in conjunction with higher redshifts, as also found in some later studies (e.g., Welter et al 1984;Kronberg et al 2008). However, Oren & Wolfe (1995) did not find any evidence of an increase of the variance of the Faraday depth as a function of the redshift, as also suggested by the recent work by Hammond et al (2012) and Pshirkov et al (2015).…”

Section: Introductionsupporting

confidence: 70%

Using rotation measure grids to detect cosmological magnetic fields: A Bayesian approach

Vacca

Oppermann

Enßlin

et al. 2016

A&A

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Determining magnetic field properties in different environments of the cosmic large-scale structure as well as their evolution over redshift is a fundamental step toward uncovering the origin of cosmic magnetic fields. Radio observations permit the study of extragalactic magnetic fields via measurements of the Faraday depth of extragalactic radio sources. Our aim is to investigate how much different extragalactic environments contribute to the Faraday depth variance of these sources. We develop a Bayesian algorithm to distinguish statistically Faraday depth variance contributions intrinsic to the source from those due to the medium between the source and the observer. In our algorithm the Galactic foreground and measurement noise are taken into account as the uncertainty correlations of the Galactic model. Additionally, our algorithm allows for the investigation of possible redshift evolution of the extragalactic contribution. This work presents the derivation of the algorithm and tests performed on mock observations. Because cosmic magnetism is one of the key science projects of the new generation of radio interferometers, we have predicted the performance of our algorithm on mock data collected with these instruments. According to our tests, high-quality catalogs of a few thousands of sources should already enable us to investigate magnetic fields in the cosmic structure.

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Section: Introductionsupporting

confidence: 70%

Using rotation measure grids to detect cosmological magnetic fields: A Bayesian approach

Vacca

Oppermann

Enßlin

et al. 2016

A&A

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“…All of these showed some evidence for an increase in the observed RM of quasars at z k1. With somewhat better RM data, and with optical absorption line data for some quasars, it was found that high column density optical and H i absorption at intervening redshifts correlated with higher levels of observed RM (e.g., Kronberg & Perry 1982;Kronberg et al 1992;Oren & Wolfe 1995). This allowed some first estimates of magnetic field strengths in distant intervening galaxy systems.…”

Section: Introductionmentioning

confidence: 90%

A Global Probe of Cosmic Magnetic Fields to High Redshifts

Kronberg

Bernet

Miniati

et al. 2008

ApJ

166

181

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Faraday rotation (rotation measure [RM]) probes of magnetic fields in the universe are sensitive to cosmological and evolutionary effects as z increases beyond $1 because of the scalings of electron density and magnetic fields, and the growth in the number of expected intersections with galaxy-scale intervenors, dN /dz. In this new global analysis of an unprecedented large sample of RMs of high-latitude quasars extending out to z $ 3:7, we find that the distribution of RM broadens with redshift in the 20Y80 rad m À2 range, despite the (1 þ z) À2 wavelength dilution expected in the observed Faraday rotation. Our results indicate that the universe becomes increasingly ''Faraday-opaque'' to sources beyond z $ 2; that is, as z increases, progressively fewer sources are found with a ''small'' RM in the observer's frame. This is in contrast to sources at z P1. They suggest that the environments of galaxies were significantly magnetized at high redshifts, with magnetic field strengths that were at least as strong within a few Gyr of the big bang as at the current epoch. We separately investigate a simple unevolving toy model in which the RM is produced by Mg ii absorber systems, and find that it can approximately reproduce the observed trend with redshift. An additional possibility is that the intrinsic RM associated with the radio sources was much higher in the past, and we show that this is not a trivial consequence of the higher radio luminosities of the high-redshift sources.

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“…The size of the absorbers has been estimated as 45 kpc, with their global magnetic fields of 2-10 µG; these are probably galactic disks and/or halos. Wolfe et al (1992) and Oren & Wolfe (1995) have argued that damped Lyα systems [i.e. putative young galactic disks (Wolfe 1988, Wolfe et al 1993] possess µG-strength global magnetic fields at z 1-2 when they are only 1-3 Gyr old.…”

Section: Magnetic Fields In High-redshift Galaxiesmentioning

confidence: 99%

GALACTIC MAGNETISM: Recent Developments and Perspectives

Beck

Brandenburg

Moss

et al. 1996

Annu. Rev. Astron. Astrophys.

966

925

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We discuss current observational and theoretical knowledge of magnetic fields, especially the large-scale structure in the disks and halos of spiral galaxies. Among other topics, we consider the enhancement of global magnetic fields in the interarm regions, magnetic spiral arms, and representations as superpositions of azimuthal modes, emphasizing a number of unresolved questions. It is argued that a turbulent hydromagnetic dynamo of some kind and an inverse cascade 1 Now at Department of Mathematics and Statistics, University of Newcastle upon Tyne, NE1 7RU, United Kingdom. 155 0066-4146/96/0915-0155$08.00 156 BECK ET AL of magnetic energy gives the most plausible explanation for the regular galactic magnetic fields. Primordial theory is found to be unsatisfactory, and fields of cosmological origin may not even be able to provide a seed field for a dynamo. Although dynamo theory has its own problems, the general form of the dynamo equations appears quite robust. Finally, detailed models of magnetic field generation in galaxies, allowing for factors such as spiral structure, starbursts, galactic winds, and fountains, are discussed and confronted with observations.

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A Faraday rotation search for magnetic fields in quasar damped LY alpha absorption systems

Cited by 92 publications

References 0 publications

Using rotation measure grids to detect cosmological magnetic fields: A Bayesian approach

Using rotation measure grids to detect cosmological magnetic fields: A Bayesian approach

A Global Probe of Cosmic Magnetic Fields to High Redshifts

GALACTIC MAGNETISM: Recent Developments and Perspectives

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