133227 - Ghost of a shell.pdf (15.65 MB)
Ghost of a shell: Magnetic fields of galactic supershell GSH 006 - 15 + 7
journal contribution
posted on 2023-05-20, 04:27 authored by Thomson, AJM, McClure-Griffiths, NM, Federrath, C, John DickeyJohn Dickey, Carretti, E, Gaensler, BM, Haverkorn, M, Kesteven, MJ, Staveley-Smith, LWe identify a counterpart to a Galactic supershell in diffuse radio polarization, and use this to determine the magnetic fields associated with this object. GSH 006 - 15 + 7 has perturbed the polarized emission at 2.3 GHz, as observed in the S-band Polarization All Sky Survey (S-PASS), acting as a Faraday screen. We model the Faraday rotation over the shell, and produce a map of Faraday depth over the area across it. Such models require information about the polarized emission behind the screen, which we obtain from the Wilkinson Microwave Anisotropy Probe (WMAP), scaled from 23 to 2.3 GHz, to estimate the synchrotron background behind GSH 006 - 15 + 7. Using the modelled Faraday thickness, we determine the magnitude and the plane-of-the-sky structure of the line-of-sight magnetic field in the shell. We find a peak line-of-sight field strength of |B∥|peak = 2.0+0.01-0.7 μG. Our measurement probes weak magnetic fields in a low-density regime (number densities of ∼ 0.4cm-3) of the ISM, thus providing crucial information about the magnetic fields in the partially-ionized phase.
History
Publication title
Monthly Notices of the Royal Astronomical SocietyVolume
479Issue
4Pagination
5620-5637ISSN
0035-8711Department/School
School of Natural SciencesPublisher
Blackwell Publishing LtdPlace of publication
9600 Garsington Rd, Oxford, England, Oxon, Ox4 2DgRights statement
Copyright 2018 The Authors. This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Repository Status
- Open