Polarized accretion shocks from the cosmic web

Vernstrom, Tessa; West, Jennifer L.; Vazza, Franco; Wittor, Denis; Riseley, C. J.; Heald, G.

doi:10.1126/sciadv.ade7233

Cited by 13 publications

(11 citation statements)

References 82 publications

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“…On larger scales magnetic fields play a more passive role, but can be a powerful tool to illuminate the tenuous intergalactic medium (e.g. Anderson et al 2021;Carretti et al 2023;Vernstrom et al 2023). Further, the origin of magnetic fields in the universe is still unknown.…”

Section: Introductionmentioning

confidence: 99%

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The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) first data release

Thomson,

McConnell,

Lenc

et al. 2023

Publ. Astron. Soc. Aust.

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The Australian SKA Pathfinder (ASKAP) radio telescope has carried out a survey of the entire Southern Sky at 887.5 MHz. The wide area, high angular resolution, and broad bandwidth provided by the low-band Rapid ASKAP Continuum Survey (RACS-low) allow the production of a next-generation rotation measure (RM) grid across the entire Southern Sky. Here we introduce this project as Spectral and Polarisation in Cutouts of Extragalactic sources from RACS (SPICE-RACS). In our first data release, we image 30 RACS-low fields in Stokes I, Q, U at 25 $^{\prime\prime}$ angular resolution, across 744–1032 MHz with 1 MHz spectral resolution. Using a bespoke, highly parallelised, software pipeline we are able to rapidly process wide-area spectro-polarimetric ASKAP observations. Notably, we use ‘postage stamp’ cutouts to assess the polarisation properties of 105912 radio components detected in total intensity. We find that our Stokes Q and U images have an rms noise of $\sim$ 80 $\unicode{x03BC}$ Jy PSF $^{-1}$ , and our correction for instrumental polarisation leakage allows us to characterise components with $\gtrsim$ 1% polarisation fraction over most of the field of view. We produce a broadband polarised radio component catalogue that contains 5818 RM measurements over an area of $\sim$ 1300 deg $^{2}$ with an average error in RM of $1.6^{+1.1}_{-1.0}$ rad m $^{-2}$ , and an average linear polarisation fraction $3.4^{+3.0}_{-1.6}$ %. We determine this subset of components using the conditions that the polarised signal-to-noise ratio is $>$ 8, the polarisation fraction is above our estimated polarised leakage, and the Stokes I spectrum has a reliable model. Our catalogue provides an areal density of $4\pm2$ RMs deg $^{-2}$ ; an increase of $\sim$ 4 times over the previous state-of-the-art (Taylor, Stil, Sunstrum 2009, ApJ, 702, 1230). Meaning that, having used just 3% of the RACS-low sky area, we have produced the 3rd largest RM catalogue to date. This catalogue has broad applications for studying astrophysical magnetic fields; notably revealing remarkable structure in the Galactic RM sky. We will explore this Galactic structure in a follow-up paper. We will also apply the techniques described here to produce an all-Southern-sky RM catalogue from RACS observations. Finally, we make our catalogue, spectra, images, and processing pipeline publicly available.

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Section: Introductionmentioning

confidence: 99%

“…2023; Vernstrom et al. 2023). Further, the origin of magnetic fields in the universe is still unknown.…”

Section: Introductionmentioning

confidence: 99%

The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) first data release

Thomson,

McConnell,

Lenc

et al. 2023

Publ. Astron. Soc. Aust.

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“…Moreover, polarisation observations have a higher dynamical range, as any unpolarised sources will not pollute the observation [263]. In a pioneering work, Vernstrom et al [264] stacked polarisation observations of cosmic filaments to detect such a signal. Indeed, they detected a polarisation fraction above 20%, which is explained by strong accretion shocks aligning the magnetic fields in the cluster's peripheries and inbetween the clusters.…”

Section: Cosmic Filaments and Voidsmentioning

confidence: 99%

Cosmic-Ray Acceleration and Magnetic Fields in Galaxy Clusters and Beyond: Insights from Radio Observations

Wittor

2023

Universe

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The discovery of diffuse radio emission in galaxy clusters proved the existence of energetic cosmic-ray electrons and cosmic magnetic fields on Mpc-scales in the Universe. Furthermore, both magnetic fields and cosmic-ray electrons are predicted to exist beyond galaxy clusters, namely, in the filaments and voids of the cosmic web. Recent detection of diffuse radio emission in intercluster bridges—the region between two merging clusters—strengthens the theory that both cosmic magnetic fields and cosmic-ray electrons exist on these large scales. Radio observations are our most powerful tool to study cosmic magnetic fields and cosmic-ray electrons in the Universe. The recent improvements in radio astronomy, including the exploration of the low-frequency radio sky, have led to the discovery of countless new radio sources, and hence a new understanding of the origin and evolution of cosmic magnetic fields and cosmic-ray electrons. In this contribution, we summarise the newest discoveries in the field. Furthermore, we discuss what these new radio observations teach us about cosmic magnetic fields and cosmic rays in galaxy clusters and beyond.

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“…To search for the diffuse emission from these intercluster regions, previous studies exploited the stacking technique of multiple individual images to increase the SNR of the sources (e.g. Clampitt et al 2016 ;Tanimura et al 2020 ;Vernstrom et al 2021 ;Tanimura et al 2022 ;Vernstrom et al 2023 ).…”

Section: T H E S Tac K I N G T E C H N I Q U Ementioning

confidence: 99%

“…Ho we ver, a follo wing-up analysis by Hodgson et al ( 2022 ) using more sensitive MWA data at 118.5 MHz does not detect the synchrotron signal in between the reported pairs of LRGs. In a recent study, Vernstrom et al ( 2023 ) reports the detection of polarized ( ≥ 20 per cent ) radio diffuse emission from the regions between the LRG pairs with the 1.4 GHz Global Magneto-Ionic Medium Surv e y (Wolleben et al 2021 ) data and the 30 GHz Planck data (Ade et al 2016 ). The LRG pairs are obtained from the Sloan Digital Sk y Surv e y (SDSS) Data Release 7 LRG Catalogue (Lopes 2007 ).…”

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confidence: 99%

A search for intercluster filaments with LOFAR and eROSITA

Hoang

Brüggen

Zhang

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Cosmological simulations predict the presence of warm hot thermal gas in the cosmic filaments that connect galaxy clusters. This gas is thought to constitute an important part of the missing baryons in the Universe. In addition to the thermal gas, cosmic filaments could contain a population of relativistic particles and magnetic fields. A detection of magnetic fields in filaments can constrain early magnetogenesis in the cosmos. So far, the resulting diffuse synchrotron emission has only been indirectly detected. We present our search for thermal and non-thermal diffuse emission from inter-cluster regions of 106 paired galaxy clusters by stacking the 0.6 − 2.3 keV X-ray and 144 MHz radio data obtained with the eROSITA telescope on board the Spectrum-Roentgen-Gamma (SRG) observatory and LOw Frequency ARray (LOFAR), respectively. The stacked data do not show the presence of X-ray and radio diffuse emission in the inter-cluster regions. This could be due to the sensitivity of the data sets and/or the limited number of cluster pairs used in this study. Assuming a constant radio emissivity in the filaments, we find that the mean radio emissivity is not higher than 1.2 × 10−44 erg s−1 cm−3 Hz−1. Under equipartition conditions, our upper limit on the mean emissivity translates to an upper limit of ∼75 nG for the mean magnetic field strength in the filaments, depending on the spectral index and the minimum energy cutoff. We discuss the constraint for the magnetic field strength in the context of the models for the formation of magnetic fields in cosmic filaments.

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Polarized accretion shocks from the cosmic web

Cited by 13 publications

References 82 publications

The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) first data release

The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) first data release

Cosmic-Ray Acceleration and Magnetic Fields in Galaxy Clusters and Beyond: Insights from Radio Observations

A search for intercluster filaments with LOFAR and eROSITA

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