scholarly journals Modeling the Ionosphere with GPS and Rotation Measure Observations

Radio Science ◽  
2018 ◽  
Vol 53 (6) ◽  
pp. 724-738 ◽  
Author(s):  
J. B. Malins ◽  
S. M. White ◽  
G. B. Taylor ◽  
K. Stovall ◽  
J. Dowell
Keyword(s):  
Rotation Measure

scholarly journals A Rotation Measure Gradient on the M87 VLA Jet

2013 ◽  
Vol 61 ◽  
pp. 07003 ◽  
Author(s):  
Juan Carlos Algaba ◽  
Keiichi Asada ◽  
Masanori Nakamura
Keyword(s):  
Rotation Measure

scholarly journals Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

2021 ◽  
Vol 38 ◽  
Author(s):  
C. S. Anderson ◽  
G. H. Heald ◽  
J. A. Eilek ◽  
E. Lenc ◽  
B. M. Gaensler ◽  
...  
Keyword(s):  
X Ray ◽  
Main Cluster ◽  
Rotation Measure ◽  
Sky Survey ◽  
Low Mass ◽  
Fornax Cluster ◽  
Depth Enhancement ◽  
Projected Distance ◽  
Density Regime ◽  
New Reservoir

Abstract We present the first Faraday rotation measure (RM) grid study of an individual low-mass cluster—the Fornax cluster—which is presently undergoing a series of mergers. Exploiting commissioning data for the POlarisation Sky Survey of the Universe’s Magnetism (POSSUM) covering a ${\sim}34$ square degree sky area using the Australian Square Kilometre Array Pathfinder (ASKAP), we achieve an RM grid density of ${\sim}25$ RMs per square degree from a 280-MHz band centred at 887 MHz, which is similar to expectations for forthcoming GHz-frequency ${\sim}3\pi$ -steradian sky surveys. These data allow us to probe the extended magnetoionic structure of the cluster and its surroundings in unprecedented detail. We find that the scatter in the Faraday RM of confirmed background sources is increased by $16.8\pm2.4$ rad m−2 within 1 $^\circ$ (360 kpc) projected distance to the cluster centre, which is 2–4 times larger than the spatial extent of the presently detectable X-ray-emitting intracluster medium (ICM). The mass of the Faraday-active plasma is larger than that of the X-ray-emitting ICM and exists in a density regime that broadly matches expectations for moderately dense components of the Warm-Hot Intergalactic Medium. We argue that forthcoming RM grids from both targeted and survey observations may be a singular probe of cosmic plasma in this regime. The morphology of the global Faraday depth enhancement is not uniform and isotropic but rather exhibits the classic morphology of an astrophysical bow shock on the southwest side of the main Fornax cluster, and an extended, swept-back wake on the northeastern side. Our favoured explanation for these phenomena is an ongoing merger between the main cluster and a subcluster to the southwest. The shock’s Mach angle and stand-off distance lead to a self-consistent transonic merger speed with Mach 1.06. The region hosting the Faraday depth enhancement also appears to show a decrement in both total and polarised radio emission compared to the broader field. We evaluate cosmic variance and free-free absorption by a pervasive cold dense gas surrounding NGC 1399 as possible causes but find both explanations unsatisfactory, warranting further observations. Generally, our study illustrates the scientific returns that can be expected from all-sky grids of discrete sources generated by forthcoming all-sky radio surveys.

scholarly journals Periastron Observations of the PSR B1259-63/SS 2883 Binary System

1996 ◽  
Vol 165 ◽  
pp. 263-269
Author(s):  
Simon Johnston
Keyword(s):  
Galactic Plane ◽  
Radio Spectrum ◽  
Wide Frequency Range ◽  
Optical Observations ◽  
Rotation Measure ◽  
Linearly Polarized ◽  
Be Star ◽  
Frequency Survey ◽  
The Magnetic Field

PSR B1259-63 is a 47-millisecond pulsar which was discovered in a high frequency survey of the galactic plane (Johnston et al. 1992a) and was subsequently found to be in a highly eccentric orbit with a main-sequence Be star known as SS 2883 (Johnston et al. 1992b). Radio observations of the pulsar led to a phase connected timing solution which predicted the epoch of periastron to be 1994 January 9 (MJD 49361.2); optical observations of the Be star led to a determination of its mass and of the size of its circumstellar disk (Johnston et al. 1994a): the star is of approximate spectral type B1e, with mass 10 M⊙ and radius 6 R⊙. If this mass is correct and the pulsar has a mass of 1.4 M⊙, then the inclination angle of the plane of the orbit with respect to the sky is 35°. This pulsar has an unusually flat radio spectrum compared to most pulsars, which makes it easily detectable up to 8.4 GHz. The narrow pulse permits dispersion and scattering measurements for studying the ionized plasma in the system. Moreover, the pulses are highly linearly polarized and permit determination of the rotation measure (RM), allowing measurements of the magnetic field along the line of sight. The 3.5-yr orbit of the pulsar around its companion thus provides us with an excellent probe of the stellar wind of the Be star over a wide frequency range.

scholarly journals A RADIO-POLARIZATION AND ROTATION MEASURE STUDY OF THE GUM NEBULA AND ITS ENVIRONMENT

2015 ◽  
Vol 804 (1) ◽  
pp. 22 ◽  
Author(s):  
C. R. Purcell ◽  
B. M. Gaensler ◽  
X. H. Sun ◽  
E. Carretti ◽  
G. Bernardi ◽  
...  
Keyword(s):  
Rotation Measure ◽  
Gum Nebula

STATIONARY SHEATH OF FARADAY ROTATION IN THE JET OF 3C 120

2010 ◽  
Vol 19 (06) ◽  
pp. 917-922
Author(s):  
JOSÉ L. GÓMEZ ◽  
MAR ROCA-SOGORB ◽  
IVÁN AGUDO ◽  
ALAN P. MARSCHER ◽  
SVETLANA G. JORSTAD
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Radio Galaxy ◽  
External Medium ◽  
Degree Of Polarization ◽  
Polarization Structure ◽  
Rotation Measure ◽  
Helical Magnetic Field ◽  
3C 120 ◽  
Two Fluid

We present a sequence of 12 monthly polarimetric multi-frequency VLBA observations of the radio galaxy 3C 120. The motion of multiple superluminal components allows the mapping of the polarization structure along most of the jet and across its width, revealing a coherent in time Faraday screen and RM-corrected polarization angles. Gradients in Faraday rotation and degree of polarization across the jet are observed, together with a localized region of high rotation measure superposed on this structure. This is explained as produced by the presence of a helical magnetic field in a two-fluid jet model, consisting of an inner emitting jet and a sheath containing nonrelativistic electrons. Interaction of the jet with the external medium would explain the confined region of enhanced Faraday rotation.

scholarly journals Faraday rotation measures of Northern hemisphere pulsars using CHIME/Pulsar

2020 ◽  
Vol 496 (3) ◽  
pp. 2836-2848 ◽  
Author(s):  
C Ng ◽  
A Pandhi ◽  
A Naidu ◽  
E Fonseca ◽  
V M Kaspi ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Faraday Rotation ◽  
Large Scale ◽  
Galactic Plane ◽  
High Signal ◽  
First Year ◽  
Systematic Analysis ◽  
Intensity Mapping ◽  
Rotation Measure ◽  
High Cadence

ABSTRACT Using commissioning data from the first year of operation of the Canadian Hydrogen Intensity Mapping Experiment’s (CHIME) Pulsar backend system, we conduct a systematic analysis of the Faraday Rotation Measure (RM) of the Northern hemisphere pulsars detected by CHIME. We present 55 new RMs as well as obtain improved RM uncertainties for 25 further pulsars. CHIME’s low observing frequency and wide bandwidth between 400 and 800 MHz contribute to the precision of our measurements, whereas the high cadence observation provides extremely high signal-to-noise co-added data. Our results represent a significant increase of the pulsar RM census, particularly regarding the Northern hemisphere. These new RMs are for sources that are located in the Galactic plane out to 10 kpc, as well as off the plane to a scale height of ∼16 kpc. This improved knowledge of the Faraday sky will contribute to future Galactic large-scale magnetic structure and ionosphere modelling.

scholarly journals WIDEBAND VERY LARGE ARRAY OBSERVATIONS OF A2256. I. CONTINUUM, ROTATION MEASURE, AND SPECTRAL IMAGING

2014 ◽  
Vol 794 (1) ◽  
pp. 24 ◽  
Author(s):  
Frazer N. Owen ◽  
Lawrence Rudnick ◽  
Jean Eilek ◽  
Urvashi Rau ◽  
Sanjay Bhatnagar ◽  
...  
Keyword(s):  
Spectral Imaging ◽  
Large Array ◽  
Very Large Array ◽  
Rotation Measure
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