Change search
ReferencesLink to record
Permanent link

Direct link
Estimating extragalactic Faraday rotation
Show others and affiliations
Number of Authors: 14
2015 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 575, A118Article in journal (Refereed) Published
Abstract [en]

Observations of Faraday rotation for extragalactic sources probe magnetic fields both inside and outside the Milky Way. Building on our earlier estimate of the Galactic contribution, we set out to estimate the extragalactic contributions. We discuss the problems involved; in particular, we point out that taking the difference between the observed values and the Galactic foreground reconstruction is not a good estimate for the extragalactic contributions. We point out a degeneracy between the contributions to the observed values due to extragalactic magnetic fields and observational noise and comment on the dangers of over-interpreting an estimate without taking into account its uncertainty information. To overcome these difficulties, we develop an extended reconstruction algorithm based on the assumption that the observational uncertainties are accurately described for a subset of the data, which can overcome the degeneracy with the extragalactic contributions. We present a probabilistic derivation of the algorithm and demonstrate its performance using a simulation, yielding a high quality reconstruction of the Galactic Faraday rotation foreground, a precise estimate of the typical extragalactic contribution, and a well-defined probabilistic description of the extragalactic contribution for each data point. We then apply this reconstruction technique to a catalog of Faraday rotation observations for extragalactic sources. The analysis is done for several different scenarios, for which we consider the error bars of different subsets of the data to accurately describe the observational uncertainties. By comparing the results, we argue that a split that singles out only data near the Galactic poles is the most robust approach. We find that the dispersion of extragalactic contributions to observed Faraday depths is most likely lower than 7 rad/m(2), in agreement with earlier results, and that the extragalactic contribution to an individual data point is poorly constrained by the data in most cases.

Place, publisher, year, edition, pages
2015. Vol. 575, A118
Keyword [en]
magnetic fields, methods: data analysis, ISM: magnetic fields
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-121701DOI: 10.1051/0004-6361/201423995ISI: 000360710400019OAI: diva2:860902
Available from: 2015-10-14 Created: 2015-10-13 Last updated: 2015-10-14Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Goobar, Ariel
By organisation
Department of PhysicsThe Oskar Klein Centre for Cosmo Particle Physics (OKC)
In the same journal
Astronomy and Astrophysics
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 13 hits
ReferencesLink to record
Permanent link

Direct link