Polarisation properties of Milky-Way-like galaxies

Abstract

(Abridged) We study the polarisation properties, magnetic field strength, and synchrotron emission scale-height of Milky-Way-like galaxies in comparison with other spiral galaxies. We use our 3D-emission model of the Milky Way Galaxy for viewing the Milky Way from outside at various inclinations as spiral galaxies are observed. When seen edge-on the synchrotron emission from the Milky Way has an exponential scale-height of about 0.74 kpc, which is much smaller than the values obtained from previous models. We find that current analysis methods overestimate the scale-height of synchrotron emission of galaxies by about 10% at an inclination of 80 degree and about 40% at an inclination of 70 degree because of contamination from the disk. The observed RMs for face-on galaxies derived from high-frequency polarisation measurements approximate to the Faraday depths (FDs) when scaled by a factor of two. For edge-on galaxies, the observed RMs are indicative of the orientation of the large-scale magnetic field, but are not well related with the FDs. Assuming energy equipartition between the magnetic field and particles for the Milky Way results in an average magnetic-field strength, which is about two times larger than the intrinsic value for a K factor of 100. The number distribution of the integrated polarisation percentages of a large sample of unresolved Milky-Way-like galaxies peaks at about 4.2% at 4.8 GHz and at about 0.8% at 1.4GHz. Integrated polarisation angles rotated by 90 degree align very well with the position angles of the major axes, implying that unresolved galaxies do not have intrinsic RMs.

10 pages, 11 figures, accepted for publication in A&A

References in corpus (14)

• Three Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Polarization Analysis
• Radio observational constraints on Galactic 3D-emission models
• The Vertical Structure of Warm Ionised Gas in the Milky Way
• Science With The Australian Square Kilometre Array Pathfinder
• Magnetism in the spiral galaxy NGC 6946: magnetic arms, depolarization rings, dynamo modes and helical fields
• Rotation Measures of Extragalactic Sources Behind the Southern Galactic Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky Way
• Modeling the Magnetic Field in the Galactic Disk using New Rotation Measure Observations from the Very Large Array
• Vertical structure of a supernova-driven turbulent magnetized ISM
• New pulsar rotation measures and the Galactic magnetic field
• Simulating polarized Galactic synchrotron emission at all frequencies, the Hammurabi code
• Cosmic rays and the magnetic field in the nearby starburst galaxy NGC253 III. Helical magnetic fields in the nuclear outflow
• A Sino-German 6 cm polarization survey of the Galactic plane III. The region from 10 degree to 60 degree longitude
• The large scale magnetic field structure of the spiral galaxy NGC 5775
• 74 MHz Discrete HII Absorption Regions Towards The Inner Galaxy

Cited by in corpus (11)

• The Tiered Radio Extragalactic Continuum Simulation (T-RECS)
• Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3-D Galactic halo magnetic field
• The effects of cosmic rays on the formation of Milky Way-mass galaxies in a cosmological context
• Is there an unaccounted excess Extragalactic Cosmic Radio Background?
• Degree of Polarization and Source Counts of Faint Radio Sources from Stacking Polarized Intensity
• Constraints from Faraday rotation on the magnetic field structure in the Galactic halo
• SKA Weak Lensing III: Added Value of Multi-Wavelength Synergies for the Mitigation of Systematics
• Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA
• Kinematic Lensing with the Roman Space Telescope
• Effects of Depolarizing Intervening Galaxies on Background Radio Emission I. Global Disk Magnetic Field
• Broad-band Radio Polarimetry of disk galaxies and AGN with KAT 7