Evidence from optical polarisation for a galactic-scale uniform magnetic field in M104

Scarrott, S. M.; White, Catherine E.; Pallister, W. S.; Solinger, Alan B.

doi:10.1038/265032a0

Cited by 12 publications

(3 citation statements)

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“…Scarrott who for many years delivered numerous results on magnetic fields using his electronographic camera methods. Up to 30% optical polarization in the halo region of M82 (Bingham et al 1976) and strong polarization along the dust lanes of M104 (Scarrott et al 1977) were published. The optical polarization in most cases indicated the presence of large-scale magnetic fields in galaxies (Elvius 1978).…”

Section: Nearby Galaxiesmentioning

confidence: 99%

Milestones in the Observations of Cosmic Magnetic Fields

Han

Wielebinski

2002

Chin. J. Astron. Astrophys.

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Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields, namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs, hereafter) of extragalactic radio sources, the pulsar RMs, radio polarization observations, as well as the newly implemented sub-mm and mm polarization capabilities. The magnetic field of the Galaxy was first discovered in 1949 by optical polarization observations. The local magnetic fields within one or two kpc have been well delineated by starlight polarization data. The polarization observations of diffuse Galactic radio background emission in 1962 confirmed unequivocally the existence of a Galactic magnetic field. The bulk of the present information about the magnetic fields in the Galaxy comes from analysis of rotation measures of extragalactic radio sources and pulsars, which can be used to construct the 3-D magnetic field structure in the Galactic halo and Galactic disk. Radio synchrotron spurs in the Galactic center show a poloidal field, and the polarization mapping of dust emission and Zeeman observation in the central molecular zone reveal a toroidal magnetic field parallel to the Galactic plane. For nearby galaxies, both optical polarization and multifrequency radio polarization data clearly show the large-scale magnetic field following the spiral arms or dust lanes. For more distant objects, radio polarization is the only approach available to show the magnetic fields in the jets or lobes of radio galaxies or quasars. Clusters of galaxies also contain widely distributed magnetic fields, which are reflected by radio halos or the RM distribution of background objects. The intergalactic space could have been magnetized by outflows or galactic superwinds even in the early universe. The Zeeman effect and polarization of sub-mm and mm emission can be used for the study of magnetic fields in some Galactic molecular clouds but it is observed only at high intensity. Both approaches together can clearly show the role that magnetic fields play in star formation and cloud structure, which in principle would be analogous to galaxy formation from protogalactic clouds. The origin of the cosmic magnetic fields is an active field of research. A primordial magnetic field has not been as yet directly detected, but its ⋆

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Section: Nearby Galaxiesmentioning

confidence: 99%

Milestones in the Observations of Cosmic Magnetic Fields

Han

Wielebinski

2002

Chin. J. Astron. Astrophys.

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“…With improved dynamic range the disk emission of NGC 4594 was detected (Bajaja et al 1988). The optical polarization observations of Scarrott et al (1977) suggested the existence of large-scale magnetic fields, but these were so far not detected in the radio frequency range.…”

Section: Introductionmentioning

confidence: 99%

Radio polarization and sub-millimeter observations of the Sombrero galaxy (NGC 4594)

Krause¹,

Wielebinski²,

Dumke

2006

A&A

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We observed the nearby early-type spiral galaxy NGC 4594 (M 104, Sombrero galaxy) with the Very Large Array at 4.86 GHz, with the Effelsberg 100-m telescope at 8.35 GHz as well as with the Heinrich Hertz Telescope at 345 GHz in radio continuum. The 4.86 and 8.35 GHz data contain polarization information and hence information about the magnetic fields: we detected a large-scale magnetic field which is to our knowledge the first detection of a large-scale magnetic field in an Sa galaxy in the radio range. The magnetic field orientation in M 104 is predominantly parallel to the disk but has also vertical components at larger z-distances from the disk. This field configuration is typical for normal edge-on spiral galaxies. The 345 GHz data pertain to the cold dust content of the galaxy. Despite the optical appearance of the object with the huge dust lane, its dust content is smaller than that of more late-type spirals.

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“…1) but this is time consuming and limited by the accuracy with which apertures can be reliably positioned. Bingham et al (1976) published one of the first imaging polarimetric observations, of the galaxy M82, shortly followed by observations of M104 (Scarrott et al 1977) and M42 (Pallister et al 1977), shown in Fig. 2a.…”

Section: Imaging Polarimetrymentioning

confidence: 99%

Imaging polarimetry as a diagnostic tool

Gledhill¹

2008

Proc. IAU

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Abstract. Some of the earliest polarimetric measurements made in astronomy were concerned with the polarization of the interstellar medium resulting from dust grains aligned in the Galactic magnetic field. More than 50 years later, polarimetry continues to be an important diagnostic of field structure on size scales ranging from planetary to galactic. The use of both linear and circular polarimetry at optical and infrared wavelengths can provide additional insights into the nature of dust particles, their alignment in magnetic fields and the field topology. Given the science benefits that polarimetry offers it is perhaps surprising that the continued existence of polarimetric facilities on current and next generation large telescopes needs to be ensured.

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Evidence from optical polarisation for a galactic-scale uniform magnetic field in M104

Cited by 12 publications

References 11 publications

Milestones in the Observations of Cosmic Magnetic Fields

Milestones in the Observations of Cosmic Magnetic Fields

Radio polarization and sub-millimeter observations of the Sombrero galaxy (NGC 4594)

Imaging polarimetry as a diagnostic tool

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