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The Fan Region at 1.5 GHz - I. Polarized synchrotron emission extending beyond the Perseus Arm
Citation
Hill, AS and Landecker, TL and Carretti, E and Douglas, K and Sun, XH and Gaensler, BM and Mao, SA and McClure-Griffiths, NM and Reich, W and Wolleben, M and Dickey, JM and Gray, AD and Haverkorn, M and Leahy, JP and Schnitzeler, DHFM, The Fan Region at 1.5 GHz - I. Polarized synchrotron emission extending beyond the Perseus Arm, Monthly Notices of the Royal Astronomical Society, 467, (4) pp. 4631-4646. ISSN 0035-8711 (2017) [Refereed Article]
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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Abstract
The Fan Region is one of the dominant features in the polarized radio sky, long thought to be a local (distance ≲500 pc) synchrotron feature. We present 1.3–1.8 GHz polarized radio continuum observations of the region from the Global Magneto-Ionic Medium Survey and compare them to maps of Hα and polarized radio continuum intensity from 0.408 to 353 GHz. The high-frequency (>1 GHz) and low-frequency (≲600 MHz) emissions have different morphologies, suggesting a different physical origin. Portions of the 1.5 GHz Fan Region emission are depolarized by ≈30 per cent by ionized gas structures in the Perseus Arm, indicating that this fraction of the emission originates ≳2 kpc away. We argue for the same conclusion based on the high polarization fraction at 1.5 GHz (≈40 per cent). The Fan Region is offset with respect to the Galactic plane, covering −5° ≲ b ≲ +10°; we attribute this offset to the warp in the outer Galaxy. We discuss origins of the polarized emission, including the spiral Galactic magnetic field. This idea is a plausible contributing factor although no model to date readily reproduces all of the observations. We conclude that models of the Galactic magnetic field should account for the ≳1 GHz emission from the Fan Region as a Galactic scale, not purely local, feature.
Item Details
| Item Type: | Refereed Article |
|---|---|
| Keywords: | polarization, ISM: magnetic fields, ISM: structure, galaxy: structure, radio continuum: ISM |
| Research Division: | Physical Sciences |
| Research Group: | Astronomical sciences |
| Research Field: | Galactic astronomy |
| Objective Division: | Expanding Knowledge |
| Objective Group: | Expanding knowledge |
| Objective Field: | Expanding knowledge in the physical sciences |
| UTAS Author: | Dickey, JM (Professor John Dickey) |
| ID Code: | 122643 |
| Year Published: | 2017 |
| Funding Support: | Australian Research Council (DP110104101) |
| Web of Science® Times Cited: | 16 |
| Deposited By: | Mathematics and Physics |
| Deposited On: | 2017-11-21 |
| Last Modified: | 2018-04-27 |
| Downloads: | 87 View Download Statistics |
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