A New Optical Polarization Catalog for the Small Magellanic Cloud: The Magnetic Field Structure

Gomes, Aiara Lobo; Magalhães, A. M.; Pereyra, A.; Rodrigues, C. V.

doi:10.1088/0004-637x/806/1/94

Cited by 12 publications

(35 citation statements)

References 61 publications

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“…Schmidt 1976;Mathewson et al 1979;Wayte 1990) strengthening the case for the existence of the pM field. More recently, Mao et al (2008) and Lobo Gomes et al (2015) note the potential alignment of the SMC magnetic field with the MB, and Mao et al (2012) argue the same for the LMC. However, all previ-ous research has been confined to high density regions in the LMC and SMC.…”

Section: The Pan-magellanic Fieldmentioning

confidence: 94%

“…Recent work by Lobo Gomes et al (2015) mapped coherent field lines in the plane-of-the-sky (B c,⊥ ) in the SMC and Wing using optical polarized starlight. They argued that there exists a significant fraction of sightlines that exhibit a magnetic field that points in the direction of the MB towards the LMC of order B ⊥ = (0.947 ± 0.079) µG.…”

Section: Estimating the Total Magnetic Field Of The Wingmentioning

confidence: 99%

“…Decades of research using optical polarized starlight has shown that polarization vectors in the plane of the sky trace out a path from the SMC along the western Bridge oriented in the direction of the LMC (Mathewson & Ford, 1970a,b;Schmidt, 1970Schmidt, , 1976Magalhaes et al, 1990;Wayte, 1990;Lobo Gomes et al, 2015). Due to the limited number of stars with which one can carry out optical polarimetry studies, all previous claims of the existence of a coherent magnetic field spanning the entire Magellanic System have had to be speculative due to the lack of information stemming from the diffuse MB.…”

Section: Introductionmentioning

confidence: 99%

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Detection of a Coherent Magnetic Field in the Magellanic Bridge through Faraday Rotation

Kaczmarek

Purcell

Gaensler

et al. 2017

Mon. Not. R. Astron. Soc.

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We present an investigation into the magnetism of the Magellanic Bridge, carried out through the observation of Faraday rotation towards 167 polarized extragalactic radio sources spanning the continuous frequency range of 1.3 − 3.1 GHz with the Australia Telescope Compact Array. Comparing measured Faraday depth values of sources 'on' and 'off' the Bridge, we find that the two populations are implicitly different. Assuming that this difference in populations is due to a coherent field in the Magellanic Bridge, the observed Faraday depths indicate a median line-of-sight coherent magnetic-field strength of B 0.3 µG directed uniformly away from us. Motivated by the varying magnitude of Faraday depths of sources on the Bridge, we speculate that the coherent field observed in the Bridge is a consequence of the coherent magnetic fields from the Large and Small Magellanic Clouds being pulled into the tidal feature. This is the first observation of a coherent magnetic field spanning the entirety of the Magellanic Bridge and we argue that this is a direct probe of a 'pan-Magellanic' field.

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Section: The Pan-magellanic Fieldmentioning

confidence: 94%

Section: Estimating the Total Magnetic Field Of The Wingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Detection of a Coherent Magnetic Field in the Magellanic Bridge through Faraday Rotation

Kaczmarek

Purcell

Gaensler

et al. 2017

Mon. Not. R. Astron. Soc.

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“…performed in the NIR/visible, among others, in NGC 891 (Montgomery & Clemens 2014), M 82 (Greaves et al 2000;Jones 2000), the SMC (Lobo Gomes et al 2015), NGC 6946 (Fendt, Beck & Neininger 1998) and the dust lane of Cen A (Scarrott et al 1996).…”

Section: Dust-induced Polarization Processesmentioning

confidence: 99%

The Interstellar Dust Properties of Nearby Galaxies

Galliano

Galametz

Jones

2018

Annu. Rev. Astron. Astrophys.

239

207

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This article gives an overview of the constitution, physical conditions and observables of dust in the interstellar medium of nearby galaxies. We first review the macroscopic, spatial distribution of dust in these objects, and its consequence on our ability to study grain physics. We also discuss the possibility to use dust tracers as diagnostic tools. We then survey our current understanding of the microscopic, intrinsic properties of dust in different environments, derived from different observables: emission, extinction, polarization, depletions, over the whole electromagnetic spectrum. Finally, we summarize the clues of grain evolution, evidenced either on local scales or over cosmic time. We put in perspective the different evolution scenarios. We attempt a comprehensive presentation of the main observational constraints, analysis methods and modelling frameworks of the distinct processes. We do not cover the dust properties of the Milky Way and distant galaxies, nor circumstellar or active galactic nucleus torus dust.

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“…Photons can also be polarised by scattering or extinction at elongated dust grains aligned in interstellar magnetic fields (e.g. Hoang & Lazarian 2014), which allows mapping these magnetic fields in the Milky Way (Fosalba et al 2002) and in the Small Magellanic Cloud (Gomes et al 2015). Elongated dust grains emit polarised emission at sub-mm wavelengths, which is useful to study the magnetic fields in molecular clouds (e.g.…”

Section: Introductionmentioning

confidence: 99%

A new method to suppress the bias in polarised intensity

Müller

Beck

Krause

2017

A&A

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Context. Computing polarised intensities from noisy data in Stokes U and Q suffers from a positive bias that should be suppressed. Aims. We aim to develop a correction method that, when applied to maps, should provide a distribution of polarised intensity that closely follows the signal from the source. Methods. We propose a new method to suppress the bias by estimating the polarisation angle of the source signal in a noisy environment with help of a modified median filter. We then determine the polarised intensity, including the noise, by projection of the observed values of Stokes U and Q onto the direction of this polarisation angle. Results. We show that our new method represents the true signal very well. If the noise distribution in the maps of U and Q is Gaussian, then in the corrected map of polarised intensity it is also Gaussian. Smoothing to larger Gaussian beamsizes, to improve the signal-to-noise ratio, can be done directly with our method in the map of the polarised intensity. Our method also works in case of non-Gaussian noise distributions. Conclusions. The maps of the corrected polarised intensities and polarisation angles are reliable even in regions with weak signals and provide integrated flux densities and degrees of polarisation without the cumulative effect of the bias, which especially affects faint sources. Features at low intensity levels like "depolarisation canals" are smoother than in the maps using the previous methods, which has broader implications, for example on the interpretation of interstellar turbulence.

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A New Optical Polarization Catalog for the Small Magellanic Cloud: The Magnetic Field Structure

Cited by 12 publications

References 61 publications

Detection of a Coherent Magnetic Field in the Magellanic Bridge through Faraday Rotation

Detection of a Coherent Magnetic Field in the Magellanic Bridge through Faraday Rotation

The Interstellar Dust Properties of Nearby Galaxies

A new method to suppress the bias in polarised intensity

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