J/MNRAS/495/2607 IGMF limits with LOFAR (O'Sullivan+, 2020)
New constraints on the magnetization of the cosmic web using LOFAR Faraday
rotation observations.
O'Sullivan S.P., Bruggen M., Vazza F., Carretti E., Locatelli N.T.,
Stuardi C., Vacca V., Vernstrom T., Heald G., Horellou C., Shimwell T.W.,
Hardcastle M.J., Tasse C., Rottgering H.
<Mon. Not. R. Astron. Soc., 495, 2607-2619 (2020)>
=2020MNRAS.495.2607O 2020MNRAS.495.2607O (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Radio sources ; Polarization
Keywords: techniques: polarimetric - galaxies: active -
galaxies: magnetic fields - large scale structure of Universe -
radio continuum: galaxies
Abstract:
Measuring the properties of extragalactic magnetic fields through the
effect of Faraday rotation provides a means to understand the origin
and evolution of cosmic magnetism. Here, we use data from the LOFAR
Two-Metre Sky Survey (LoTSS) to calculate the Faraday rotation measure
(RM) of close pairs of extragalactic radio sources. By considering the
RM difference (ΔRM) between physical pairs (e.g. double-lobed
radio galaxies) and non-physical pairs (i.e. close projected sources
on the sky), we statistically isolate the contribution of
extragalactic magnetic fields to RM along the line of sight between
non-physical pairs. From our analysis, we find no significant
difference between the RM distributions of the physical and
non-physical pairs, limiting the excess Faraday rotation contribution
to <1.9rad/m2 (∼95 per cent confidence). We use this limit with a
simple model of an inhomogeneous universe to place an upper limit of
4nG on the cosmological co-moving magnetic field strength on Mpc
scales. We also compare the RM data with a more realistic suite of
cosmological magnetohydrodynamical simulations that explore different
magnetogenesis scenarios. Both magnetization of the large-scale
structure by astrophysical processes such as galactic and AGN
outflows, and simple primordial scenarios with seed magnetic field
strengths <0.5nG cannot be rejected by the current data; while
stronger primordial fields or models with dynamo amplification in
filaments are disfavoured.
Description:
Faraday rotation measure (RM) data for 349 pairs of radio source
components with angular separations between 0.33 and 20-arcmin.
The data presented here were obtained using the LOFAR Two-Metre Sky
Survey (LoTSS), with a frequency range of 120 to 168MHz and a
spectral resolution of 97.6kHz, between May 2014 and May 2020. The
quoted RM errors are the nominal error calculated from the measurement
noise and do not include systematic errors that would be relevant for
comparison with other observations. The quoted RM errors are
appropriate for the RM difference between close pairs, while for other
applications we recommend adding a systematic uncertainty of
approximately 0.05rad/m2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 49 698 Coordinates, angular separation and RM values
of all sources in the sample
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See also:
https://lofar-surveys.org : LOFAR Home Page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID RM pair identifier NNNp (1)
6- 7 I2 h RAh Right ascension (J2000)
9- 10 I2 min RAm Right ascension (J2000)
12- 16 F5.2 s RAs Right ascension (J2000)
18 A1 --- DE- Declination sign (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 29 F5.2 arcsec DEs Declination (J2000)
31- 35 F5.2 arcmin Sep Angular separation between pairs
37- 43 F7.3 rad/m2 RM Faraday rotation measure
45- 49 F5.3 rad/m2 e_RM Faraday rotation measure uncertainty (2)
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Note (1): The ID column indicates classification as a random or physical pair
with the r or p suffix.
Note (2): The nominal RM error value does not include the error from the
ionosphere RM correction, and thus is only valid in the case of taking the
difference in RM between pairs in this catalogue.
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Acknowledgements:
Shane O'Sullivan, shane.osullivan(at)dcu.ie
(End) Patricia Vannier [CDS] 23-Jun-2022