J/MNRAS/515/256 Comoving IGMF redshift evolution (Pomakov+, 2022)
The redshift evolution of extragalactic magnetic fields.
Pomakov V.P., O'Sullivan S.P., Brueggen M., Vazza F., Carretti E.,
Heald G.H., Horellou C., Shimwell T., Shulevski A., Vernstrom T.
<Mon. Not. R. Astron. Soc. 515, 256 (2022)>
=2022MNRAS.515..256P 2022MNRAS.515..256P (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:
Faraday rotation studies of distant radio sources can constrain the
evolution and the origin of cosmic magnetism. We use data from the
LOFAR Two-Metre Sky Survey: Data Release 2 (LoTSS DR2) to study the
dependence of the Faraday rotation measure (RM) on redshift. By
focusing on radio sources that are close in terms of their projection
on the sky, but physically unrelated ('random pairs'), we measure the
RM difference, ΔRM, between the two sources. Thus, we isolate the
extragalactic contribution to ΔRM from other contributions. We
present a statistical analysis of the resulting sample of random pairs
and find a median absolute RM difference
|ΔRM|=(1.79±0.09)rad/m2, with |ΔRM| uncorrelated both
with respect to the redshift difference of the pair and the redshift
of the nearer source, and a median excess of random pairs over
physical pairs of (1.65±0.10)rad/m2. We seek to reproduce this
result with Monte Carlo simulations assuming a non-vanishing seed
cosmological magnetic field and a redshift evolution of the comoving
magnetic field strength that varies as (1+z)-gamma. We find the
best-fitting results B0=Bcomoving(z=0)≲(2.0±0.2)nG and gamma
≲4.5±0.2 that we conservatively quote as upper limits due to an
unmodelled but non-vanishing contribution of local environments to the
RM difference. A comparison with cosmological simulations shows our
results to be incompatible with primordial magnetogenesis scenarios
with uniform seed fields of order nG.
Description:
Faraday rotation measure (RM) and redshift data for 514 pairs of radio
source components with angular separations between 0.33 and 30-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
rmpairs.dat 326 514 Coordinates, RM, redshift and angular
separation of all sources in the sample
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See also:
J/A+A/659/A1 : LOFAR Two-metre Sky Survey (LoTSS) DR2 (Shimwell+, 2022)
Byte-by-byte Description of file: rmpairs.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RA1deg Right ascension of source 1 in pair (J2000)
13- 22 F10.7 deg DE1deg Declination of source 1 in pair (J2000)
24- 31 F8.3 rad/m2 RM1 Faraday rotation measure of source 1 in pair
33- 53 F21.19 rad/m2 e_RM1 Faraday rotation measure uncertainty (1)
55- 76 F22.18 rad/m2 RRM1 Residual rotation measure of source 1
in pair (2)
78- 97 F20.16 rad/m2 GRM1 Galactic rotation measure of source 1 in pair
99-117 F19.17 rad/m2 e_GRM1 Galactic rotation measure uncertainty
119-138 F20.18 --- z1 Redshift of source 1 in pair
140 I1 --- n_z1 [0/1] 0: Photometric redshift,
1: spectroscopic redshift
144-148 I5 --- ID1 Unique identifier of source 1 in pair
152-162 F11.7 deg RA2deg Right ascension of source 2 in pair (J2000)
164-173 F10.7 deg DE2deg Declination of source 2 in pair (J2000)
175-182 F8.3 rad/m2 RM2 Faraday rotation measure of source 2 in pair
184-204 F21.19 rad/m2 e_RM2 Faraday rotation measure uncertainty (1)
206-227 F22.18 rad/m2 RRM2 Residual rotation measure of source 2
in pair (2)
229-248 F20.16 rad/m2 GRM2 Galactic rotation measure of source 2 in pair
250-268 F19.17 rad/m2 e_GRM2 Galactic rotation measure uncertainty
270-289 F20.18 --- z2 Redshift of source 2 in pair
291 I1 --- n_z2 [0/1] 0: Photometric redshift,
1: spectroscopic redshift
295-299 I5 --- ID2 Unique identifier of source 2 in pair
303 I1 --- RandPhys [0/1] Pair type identifier.
0: random pair, 1: physical pair
307-326 F20.15 arcsec Sep Angular separation between pairs
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Note (1): The nominal RM error value does not include the error from the
ionosphere RM correction (∼0.05rad/m2), and thus is only valid in the
case of taking the difference in RM between pairs in this catalogue.
Note (2): Obtained by subtraction of the average GRM with a disc of diameter
1 degree, using v2 of the Galactic Faraday rotation sky (see paper).
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Acknowledgements:
Shane O'Sullivan, shane.osullivan(at)dcu.ie
Valentin Pomakov, valentin.pomakov(at)rwth-aachen.de
(End) Patricia Vannier [CDS] 01-Aug-2022