Investigation of the Radial Profile of Galactic Magnetic Fields using Rotation Measure of Background Quasars

Abstract

Probing magnetic fields in high-redshift galactic systems is crucial to investigate galactic dynamics and evolution. Utilizing the rotation measure of the background quasars, we have developed a radial profile of the magnetic field in a typical high-$z$ galaxy. We have compiled a catalog of 59 confirmed quasar sightlines, having one intervening Mg \rom{2} absorber in the redshift range $0.372\le z_{\text{abs}}\le 0.8$. The presence of the foreground galaxy is ensured by comparing the photometric and spectroscopic redshifts within $3{\sigma }_{z-\text{photo}}$ and visual checks. These quasar line-of-sights (LoS) pass through various impact parameters (D) up to $160$ kpc, covering the circumgalactic medium of a typical Milky-Way type galaxy. Utilizing the residual rotation measure (RRM) of these sightlines, we estimated the excess in RRM dispersion, ${\sigma }_{\text{ex}}^{\text{RRM}}$. We found ${\sigma }_{\text{ex}}^{\text{RRM}}$ decreases with increasing D. We translated ${\sigma }_{\text{ex}}^{\text{RRM}}$ to average LoS magnetic field strength, $⟨B_{\Vert }⟩$ by considering a typical electron column density. Consequently, the decreasing trend is sustained in the magnetic field. In particular for sightlines with $\text{D}\le 50$ kpc and $\text{D}>50$ kpc, $⟨B_{\Vert }⟩$ is found to be $2.39\pm 0.7\mu$G and $1.67\pm 0.38\mu$G, respectively. This suggests a clear indication of varying magnetic field from the disk to the circumgalactic medium. This work provides a methodology that, when applied to ongoing and future radio polarisation surveys such as LOFAR and SKA, promises to significantly enhance our understanding of magnetic field mapping in galactic systems.

Published in JCAP

References in corpus (17)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Circumgalactic Medium
• Strong magnetic fields in normal galaxies at high redshifts
• A Unified Catalog of Radio Objects Detected by NVSS, FIRST, WENSS, GB6, and SDSS
• A Global Probe of Cosmic Magnetic Fields to High Redshifts
• Halo Gas Cross Sections And Covering Fractions of MgII Absorption Selected Galaxies
• Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study
• Faraday Rotation from Magnesium II Absorbers towards Polarized Background Radio Sources
• CHANG-ES XV: Large-scale magnetic field reversals in the radio halo of NGC 4631
• Seed magnetic fields in turbulent small-scale dynamos
• Detection of magnetic fields in the circumgalactic medium of nearby galaxies using Faraday rotation
• Magnetic fields in the Milky Way from pulsar observations: effect of the correlation between thermal electrons and magnetic fields
• The Chemical and Ionization Conditions in Weak Mg II Absorbers
• Constraining Magnetic Fields in the Circumgalactic Medium
• The Kinematic Evolution of Strong MgII Absorbers
• Probing magnetic fields in the circumgalactic medium using polarization data from MIGHTEE
• Global enhancement and structure formation of the magnetic field in spiral galaxies

Cited by in corpus (2)

• Magnetised CGM Gas at z~1 revealed by SPICE-RACS
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