Radio Polarisation Study of High Rotation Measure AGNs

Ki, Yik; Mao, Sui Ann; Basu, Aritra; Heiles, Carl; West, Jennifer L.

doi:10.3390/galaxies5040066

Cited by 4 publications

(4 citation statements)

References 19 publications

(34 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Faraday rotation in a magneto-ionic medium produces various external or internal depolarization processes (e.g., Burn 1966;Tribble 1991;Sokoloff et al 1998). These provide a unique and critical diagnostic of the magneto-ionic medium, but only when observed over a wide frequency range with nearcontinuous frequency coverage (e.g., O'Sullivan et al 2012;Anderson et al 2016;Ma et al 2017;Pasetto et al 2018, Figure 3). Until a few years ago, polarimetric studies have either relied on a small number of widely spaced narrow bands, or have observed over a continuous but relatively narrow (∼10%) fractional bandwidth.…”

Section: Polarization In Vlassmentioning

confidence: 99%

The Karl G. Jansky Very Large Array Sky Survey (VLASS). Science Case and Survey Design

Lacy

Baum

Chandler

et al. 2020

PASP

470

264

View full text Add to dashboard Cite

The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with a unique combination of high angular resolution (≈2 5), sensitivity (a 1σ goal of 70 μJy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2-4 GHz). The first observations began in 2017 September, and observing for the survey will finish in 2024. VLASS will use approximately 5500 hr of time on the Karl G. Jansky Very Large Array (VLA) to cover the whole sky visible to the VLA (decl. >−40°), a total of 33 885deg 2. The data will be taken in three epochs to allow the discovery of variable and transient radio sources. The survey is designed to engage radio astronomy experts, multi-wavelength astronomers, and citizen scientists alike. By utilizing an "on the fly" interferometry mode, the observing overheads are much reduced compared to a conventional pointed survey. In this paper, we present the science case and observational strategy for the survey, and also results from early survey observations.

show abstract

Section: Polarization In Vlassmentioning

confidence: 99%

The Karl G. Jansky Very Large Array Sky Survey (VLASS). Science Case and Survey Design

Lacy

Baum

Chandler

et al. 2020

PASP

470

264

View full text Add to dashboard Cite

show abstract

“…They could have been detected with S-PASS/ATCA, and also with TSS09. However, in TSS09, such sources suffer from strong depolarization (see figure 1 in the paper by Taylor et al, Stil &Taylor 2007, andPasetto et al 2016) and they can be misinterpreted because of nπ ambiguities in polarization angle (see, e.g., Ma et al 2017). In Fig.…”

Section: Resultsmentioning

confidence: 99%

S-PASS/ATCA: a window on the magnetic universe in the Southern hemisphere

Schnitzeler

Carretti

Wieringa

et al. 2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present S-PASS/ATCA, the first wide-band radio polarimetry survey of compact sources in the southern sky. We describe how we selected targets for observations with the Australia Telescope Compact Array (ATCA) in the 16 cm band (1.3 -3.1 GHz), our observing and calibration strategy, how we analysed the data, and how we tested the quality of the data. The data are made publicly available. The survey contains on average one source per five square degrees and has an angular resolution at 2.2 GHz of ∼ 2 ′ ×1 ′ . Sources with |RM|s > 150 rad m −2 are seen towards the Galactic plane and bright H ii regions, but are rare elsewhere on the sky. Sightlines that are separated by up to 3 ′ show very similar RMs. Based on this observation, we argue that the Galactic foreground is the dominant contributor to RM, confirming previous results, and that the sources must have very simple distributions of Faraday-rotating and synchrotronemitting media. Many sources that emit at a single RM have a spectral index in linear polarization that is (very) different from the spectral index in Stokes I. Analysing ratios of flux densities Q/I and U/I (to correct for spectral index effects) then leads to erroneous results. About 80 per cent of sightlines in our survey are dominated by emission at only one RM. Therefore, RMs that were determined previously from narrow-band observations at these frequencies are still safe to use.

show abstract

“…Traditionally, Φ is determined by observing ψ at a few wavelengths and fitting a linear relationship as a function of λ 2 . This method suffers from a number of problems including nπ ambiguities and being constrained to high signal-to-noise (S/N) polarization observations (Ma et al 2017). This is especially true when Φ is large as Q and U must be measured in narrow channels.…”

Section: Rm Synthesismentioning

confidence: 99%

Disentangling Magnetic Fields in NGC 6946 with Wide-band Polarimetry

Williams,

Heald,

Wilcots

et al. 2024

ApJ

View full text Add to dashboard Cite

We present λ13 cm polarization observations of the nearby spiral galaxy NGC 6946 with the Westerbork Synthesis Radio Telescope (WSRT) to examine the nearside halo magnetic fields. Despite λ13 cm exhibiting similar two-dimensional morphology as observed at longer (λ18–22 cm) or shorter (λ3 and λ6 cm) wavelengths, more complete frequency coverage will be required to explain the gap in polarization in the southwest quadrant of the galaxy. We fit models of the turbulent and coherent line-of-sight magnetic fields to the fractional degree of linearly polarized emission at λ3, λ6, λ13, λ18, and λ22 cm from observations taken with the WSRT, Karl G. Jansky Very Large Array, and Effelsberg telescopes. The results favor a multilayer turbulent magneto-ionized medium consistent with current observations of edge-on galaxies. We constrain the physical properties of the synchrotron-emitting thin and thick disks (scale heights of 300 pc and 1.4 kpc, respectively) along with the thermal thick disk and halo (scale heights of 1 and 5 kpc, respectively). Our preferred model indicates a clumpy and highly turbulent medium within 1 kpc of the midplane, and a diffuse extraplanar layer with a substantially lower degree of Faraday depolarization. In the halo, we estimate a regular magnetic field strength of 0.4–2.2 μG and that turbulence and a total magnetic field strength of ∼6 μG result in a Faraday dispersion of σ RM = 4–48 rad m−2. This work is an example of how the advanced capabilities of modern radio telescopes are opening a new frontier for the study of cosmic magnetism.

show abstract

Radio Polarisation Study of High Rotation Measure AGNs

Cited by 4 publications

References 19 publications

The Karl G. Jansky Very Large Array Sky Survey (VLASS). Science Case and Survey Design

The Karl G. Jansky Very Large Array Sky Survey (VLASS). Science Case and Survey Design

S-PASS/ATCA: a window on the magnetic universe in the Southern hemisphere

Disentangling Magnetic Fields in NGC 6946 with Wide-band Polarimetry

Contact Info

Product

Resources

About