arXiv subjects

A. Pagliotta

Publications and source records attributed to A. Pagliotta.

2 recordsLinked to original sources

arXiv2026

Magnetic fields at the dawn of structure formation I. The CARLA J1510+5958 proto-cluster

Magnetic fields are a fundamental ingredient of the Universe, influencing the formation and evolution of cosmic structures. While magnetic fields in local galaxy clusters have been studied, their origin, amplification, and strength at high redshift are poorly understood. Proto-clusters represent the early stages of galaxy cluster formation, ideal for investigating the early magnetisation of the intra-cluster medium (ICM). We present a study of CARLA J1510+5958 proto-cluster at z = 1.72, observed with the JVLA in the L-band (1-2 GHz). We aim to investigate the magnetic field strength and structure in the proto-ICM and the role of AGN in magnetising the environment during early cluster formation. We analyse Faraday rotation on the polarised emission from the central radio-loud AGN using the Rotation Measure (RM) synthesis and QU fitting technique. We further interpret the observations with 3D simulations of gas density and turbulent magnetic fields, varying AGN orientation and path length. The two AGN lobes show different polarisation properties. The Western lobe exhibits a uniform RM (average $-115 \pm 32\text{ rad m}^{-2}$, dispersion $36 \pm 11\text{ rad m}^{-2}$), indicating a locally ordered magnetic field likely compressed by the lobe, while the Eastern lobe is depolarised. Although the asymmetry indicates a turbulent, magnetised medium, simulations rule out a purely isotropic random field for the Western lobe RM distribution. The QU fitting further suggests an internal Faraday component, interpreted as magnetised relativistic plasma from the lobe mixed with the surrounding gas, indicating possible magnetisation of the ambient medium by the AGN. From this asymmetry, we constrain the average physical magnetic field in the proto-ICM to a lower limit of 0.4 $\mu$G. These results confirm a magnetised proto-ICM at z = 1.72, proving early field amplification during cluster assembly.

astro-ph.CO↗

arXiv2025

Constraining the magnetic field in the galaxy cluster Abell 2142 using MeerKAT L-band polarisation data

Magnetic fields permeate the Universe, including galaxy clusters, and affect the thermodynamical properties of the intra-cluster medium (ICM). Cosmological simulations predict that seed magnetic fields are amplified up to the $\mu$G-level in the ICM, but the magnetic field strength and structure have been studied in only a few clusters. Abell 2142 is a local massive cluster that shows evidence of a post-merger dynamical state. In this work, we aim to constrain the magnetic field intensity, radial profile and power spectrum within its ICM, providing key insights into the nature of this non-thermal component in galaxy clusters. We present MeerKAT observations of Abell 2142 in the L-band (872-1712 MHz), imaged in polarisation for the first time with this purpose. We derive the Rotation Measure (RM) from the radio galaxies' polarised emission by applying the RM synthesis technique and analyse both the RM and fractional polarisation ($\mathrm{F_p}$). To investigate the magnetic field distribution within the ICM, we compare our results with mock RM maps generated from 3D simulations of the cluster. We find that the RM dispersion, $\sigma_{\mathrm{RM}}$, decreases with projected radius, whereas the $\mathrm{F_p}$ increases. Both trends suggest that the magnetic field intensity decreases at larger distances from the cluster center, in agreement with studies on other clusters. Assuming that the magnetic field energy density scales with the gas thermal energy ($B \propto n_e^{0.5}$), a magnetic field with a power spectrum ranging from scales between 7 and 470 kpc, with peak at $\sim 140$ kpc and mean central strength of $9.5 \pm 1.0 \ \mu$G, provides the best fit to our data. The high central magnetic field lies at the upper end of the range observed in other systems and supports the possibility of an hadronic contribution to the diffuse radio emission previously detected at the cluster center.

astro-ph.CO↗