J/A+A/694/A44 RM catalogue of the Chandra Planck clusters (Osinga+, 2025)
Probing cluster magnetism with embedded and background radio sources
in Planck clusters.
Osinga E., van Weeren R.J., Rudnick L., Andrade-Santos F., Bonafede A.,
Clarke T., Duncan K., Giacintucci S., Roettgering H.J.A.
<Astron. Astrophys. 694, A44 (2025)>
=2025A&A...694A..44O 2025A&A...694A..44O (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Radio continuum ; Magnetic fields ;
Polarization
Keywords: magnetic fields - polarization - methods: observational -
galaxies: clusters: general -
galaxies: clusters, intracluster medium - radio continuum: general
Abstract:
Magnetic fields remain an elusive part of the content of galaxy
clusters. Faraday rotation and depolarisation of extragalactic radio
sources are useful probes, but the limited availability of polarised
radio sources necessitates the stacking of clusters to study average
magnetic field properties. We recently presented a Karl G. Jansky Very
Large Array survey of the 124 most massive Planck clusters at low
redshift (z<0.35), finding a clear depolarisation trend with the
cluster impact parameter, with sources at smaller projected distances
to the cluster centre showing more depolarisation. In this study, we
combine the depolarisation information with the observed rotation
measure (RM) and present an investigation of the average magnetic
field properties of the sample, using both background sources and
sources embedded in clusters. We observe a significant increase in the
RM scatter, σRRM, closer to the cluster centres. Averaging all
124 clusters, we find a scatter within R500 of
σRRM=209±37rad/m2, with background sources and cluster
members showing similar values (200±33 and 219±66rad/m2,
respectively). In the simple assumption of a uniform amplitude
magnetic field with a single fluctuation scale {LAMBDA}c, this
translates to an average magnetic field strength of
2({LAMBDA}c/10kpc)-0.5uG. The profile of σRRM as a
function of the projected radius is inconsistent with a model that has
a simple scaling B∝neeta, with an observed deficit near
the centre of clusters possibly caused by the fact that the highest RM
sources near the centre of clusters are depolarised. Combining
depolarisation and RM in a full forward model, we find that the
magnetic field power spectrum roughly agrees with the Kolmogorov
value, but that none of the Gaussian random field models can fully
explain the observed relatively flat profiles. This implies that more
sophisticated models of cluster magnetic fields in a cosmological
context are needed.
Description:
In this paper, we investigate the RM and depolarisation of radio
sources inside and behind clusters in a sample of 124 massive clusters
at z<0.35 observed with the Karl G. Jansky Very Large Array. We
compare Gaussian random field models to the data in a forward
modelling approach.
We present VLA L-band (1-2GHz) observations of 124 Planck clusters at
z<0.35 and DEC>-40 deg (VLA project code 15A-270). The observations
were taken in the B(nA) array configuration for about 40 minutes per
target. These catalogues contain the results of the source finding in
both full intensity (Stokes I) and linearly polarised intensity, as
well as the polarisation properties determined from QU-fitting. They
also contain additional information about the location of the optical
host and redshift.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec1.dat 427 819 Polarised source catalogue
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Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RAdeg Source right ascension (J2000) (RA)
13- 23 F11.7 deg DEdeg Source declination (J2000) (DEC)
25- 34 F10.7 deg e_RAdeg ?=-1 Source right ascension uncertainty
(E_RA)
36- 45 F10.7 deg e_DEdeg ?=-1 Source declination uncertainty
(E_DEC)
47- 52 F6.3 arcsec Maj Source major axis (Maj)
54- 59 F6.3 arcsec Min Source minor axis (Min)
61- 67 F7.4 arcsec e_Maj ?=-1 Source major axis uncertainty
(E_Maj)
69- 75 F7.4 arcsec e_Min ?=-1 Source minor axis uncertainty
(E_Min)
77- 83 F7.3 deg PA [] Source position angle (PA)
85- 92 F8.3 deg e_PA ?=-1 Source position angle uncertainty
(E_PA)
94-100 F7.5 --- PFExtDepol ?=- Best fit intrinsic polarisation
fraction (PolFrac_ExtDepol)
102-110 F9.6 --- e_PFExtDepol []?=- Lower uncertainty on PolFracER
(PolFracErrNegExtDepol)
112-119 F8.6 --- E_PFExtDepol ?=- Upper uncertainty on PolFracER
(PolFracErrPosExtDepol)
121-126 F6.4 rad IAExtDepol ?=- Best fit intrinsic polarisation
angle (IntrAngl_ExtDepol)
128-134 F7.4 rad e_IAExtDepol []?=- Lower uncertainty on IAExtDepol
(IntrAnglErrNegExtDepol)
136-141 F6.4 rad E_IAExtDepol ?=- Upper uncertainty on IAExtDepol
(IntrAnglErrPosExtDepol)
143-151 F9.3 rad/m2 RMExtDepol ?=- Best fit RM (RM_ExtDepol)
153-162 F10.4 rad/m2 e_RMExtDepol []?=- Lower uncertainty on RMExtDepol
(RMErrNegExtDepol)
164-173 F10.5 rad/m2 E_RMExtDepol ?=- Upper uncertainty on RMExtDepol
(RMErrPosExtDepol)
175-186 E12.6 rad/m2 sigRMExtDepol ?=- Best fit depolarisation (sigmaRM)
(sigmaRM_ExtDepol)
188-199 E12.6 rad/m2 e_sigRMExtDepol []?=- Lower uncertainty on sigRMExtDepol
(sigmaRMErrNegExtDepol)
201-212 E12.6 rad/m2 E_sigRMExtDepol ?=- Upper uncertainty on sigRMExtDepol
(sigmaRMErrPosExtDepol)
214-220 F7.2 mJy I0ExtDepol ?=- Best fit I0 (I0ExtDepol)
222-228 F7.3 mJy e_I0ExtDepol []?=- Lower uncertainty on I0ExtDepol
(I0ErrNeg_ExtDepol)
230-235 F6.3 mJy E_I0ExtDepol ?=- Upper uncertainty on I0ExtDepol
(I0ErrPos_ExtDepol)
237-241 F5.2 --- aExtDepol ?=- Best fit spectral index (a_ExtDepol)
243-248 F6.3 --- e_aExtDepol []?=- Lower uncertainty on aExtDepol
(aErrNegExtDepol)
250-254 F5.3 --- E_aExtDepol ?=- Upper uncertainty on aExtDepol
(aErrPosExtDepol)
256-264 F9.4 --- chi2QU ?=- Chi2 value for QU fit (chi2_QU)
266-272 F7.5 --- bestz ?=- Best-estimate redshift (z) (bestz)
274-280 F7.5 --- e_bestz ?=- Uncertainty on bestz (bestz_err)
282 I1 --- r_bestz [0/4]? Source of bestz
(bestz_source) (1)
284-292 F9.7 --- rnorm ?=- Radius/R500 to cluster centre
(rnorm)
294-303 F10.8 amin thetap Radius to pointing centre (theta_p)
305-317 A13 --- Cluster Name of target cluster, GLLL.ll+BB.bb
(Cluster)
319-327 F9.5 deg RAOdeg ?=- Best estimate optical host
right ascension (ra_opthost)
329-337 F9.5 deg DEOdeg ?=- Best estimate host declination
(dec_opthost)
339 I1 --- MultiFlag [0/1] If Source is multicomponent
(MultiCompFlag)
341 I1 --- Flagged [0/1] If Source was flagged (Flagged)
343-393 A51 --- Note Additional notes (Note)
395-403 F9.3 rad/m2 RRM ?=- Best fit RM minus galactic
contribution (RRM)
405-413 F9.4 rad/m2 e_RRM ?=- Lower uncertainty (RRM_ErrNeg)
415-423 F9.4 rad/m2 E_RRM ?=- Upper uncertainty (RRM_ErrPos)
425 I1 --- behind [0/1] Source is behind target cluster
(behind)
427 I1 --- inside [0/1] Source is inside target cluster
(inside)
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Note (1): References as follows:
0 = NED/Literature (spectroscopic)
1 = SDSS (spectroscopic)
2 = Legacy (photometric)
3 = PANSTARRS (photometric)
4 = SDSS (photometric)
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Acknowledgements:
Erik Osinga, erik.osinga(at)utoronto.ca
(End) Erik Osinga [Univ. of Toronto], Patricia Vannier [CDS] 18-Dec-2024