Rotation Measures of Extragalactic Sources behind the Southern Galactic Plane: New Insights into the Large‐Scale Magnetic Field of the Inner Milky Way

Brown, J. C.; Haverkorn, M.; Gaensler, B. M.; Taylor, A. R.; Bizunok, N.S.; McClure-Griffiths, N. M.; Dickey, John M.; Green, Anne

doi:10.1086/518499

Cited by 225 publications

(317 citation statements)

References 30 publications

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“…Using RMs of 554 southern pulsars mostly in the first and fourth Galactic quadrants, Han et al (2006) conclude that the field in the spiral arms interior to the Sun is counterclockwise (CCW) as viewed from the Galactic North Pole (a convention that we A&A 513, A65 (2010) follow), while the field in the interarm regions is most likely clockwise (CW). Brown et al (2007) used RMs of 148 EGS close to the Galactic plane (|b| ≤ 1.5 • ) in the fourth Galactic quadrant, in combination with RMs of 120 pulsars in the same region. They concluded that the best-fit model to those data has a CW field everywhere, except in the Crux-Scutum arm and in the Molecular Ring.…”

Section: Rm ∝mentioning

confidence: 99%

“…We used the 148 EGS observed and used by Brown et al (2007) in the Galactic longitude range 253 • ≤ l ≤ 358 • and with Galactic latitudes |b| ≤ 1.…”

Section: The Datamentioning

confidence: 99%

“…Somewhat surprisingly, these two effects have never been fully taken into account in discussions of the large-scale component of the Galactic magnetic field based on RM estimates of PSR and/or EGS (see e.g., Rand & Kulkarni 1989;Rand & Lyne 1994;Indrani & Deshpande 1999;Han et al 1999;Frick et al 2001;Han et al 2006;Brown et al 2007;Men et al 2008;Vallée 2008a). From time to time, one finds references to unexpected deviations from smoothness in the RM-distributions, as e.g., in the so-called "Carina-anomaly" mentioned by Han et al (2006).…”

Section: The Reliability Of the Rm Estimatesmentioning

confidence: 99%

“…Notwithstanding these difficulties, several groups have tried to map the large-scale Galactic field, using observations of the rotation measures (RM) of pulsars (e.g., Weisberg et al 2004;Han et al 2006;Noutsos et al 2008;Men et al 2008;Vallée 2008a) and/or extragalactic radio sources (Brown et al 2007). An intrinsic problem in the use of RM is that its information on the l.o.s.-component of the magnetic field, B , is coupled with the density of free electrons n e , since…”

Section: Introductionmentioning

confidence: 99%

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The large-scale magnetic field in the fourth Galactic quadrant

Nota¹,

Katgert²

2010

A&A

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Aims. We have re-examined the published rotation measures (RMs) of extragalactic point sources and pulsars with |b| < 3 • to study the magnetic field in the fourth Galactic quadrant. Methods. We reduced the influence of structure in electron density as much as possible by excluding objects for which Hα-data indicate large fluctuations in n e somewhere along the line of sight. We also excluded objects for which the RM may have been significantly "corrupted" by an intervening supernova remnant. We modeled RM(l), the longitude dependence of RM of the unaffected extragalactic sources and pulsars. We assumed several geometries for the large-scale field. All but one of those are based on logarithmic spiral arms (with various pitch angles and widths), while one has circular symmetry. We also made different assumptions about the large-scale n e -distribution. Results. The data suggest the following generic behaviour of the large-scale field in the 4th Galactic quadrant. The field is most likely organized along logarithmic spiral arms and shows two significant reversals: from the Norma arm (CCW field) to the Norma-Crux interarm region (CW field), and from the Norma-Crux interarm region to the Crux arm (CCW field). The present data do not constrain the field in and beyond the Crux-Carina interarm region. Although the models give a good description of the global character of RM(l), individual RM-estimates deviate by typically 15 times their measurement errors. We argue that these large deviations are most likely due to the "small-scale" field that dominates on scales of up to several hundred pc. Conclusions. The picture that emerges is thus of a field that has significant structure on smaller scales, but for which the average values in arms and interarm regions are nevertheless well-defined. In addition, this smaller-amplitude large-scale field appears to reverse at each arm-interarm boundary that we can study with the present data. We briefly discuss the link between these results and theoretical predictions.

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Section: Rm ∝mentioning

confidence: 99%

“…We used the 148 EGS observed and used by Brown et al (2007) in the Galactic longitude range 253 • ≤ l ≤ 358 • and with Galactic latitudes |b| ≤ 1.…”

Section: The Datamentioning

confidence: 99%

Section: The Reliability Of the Rm Estimatesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The large-scale magnetic field in the fourth Galactic quadrant

Nota¹,

Katgert²

2010

A&A

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“…In recent years extensive efforts have been made to enlarge the RM samples of background sources at low Galactic latitudes (e.g. Brown et al 2007, Van Eck et al 2011. The RM data behind the Galactic disk (see Fig.1 of Han 2013) are much denser in the outer Galaxy than in the inner Galaxy.…”

Section: Magnetic Fields In the Galactic Diskmentioning

confidence: 99%

Magnetic fields in our Milky Way Galaxy and nearby galaxies

Han

2012

Proc. IAU

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Abstract. Magnetic fields in our Galaxy and nearby galaxies have been revealed by starlight polarization, polarized emission from dust grains and clouds at millimeter and submillimeter wavelength, the Zeeman effect of spectral lines or maser lines from clouds or clumps, diffuse radio synchrotron emission from relativistic electrons in interstellar magnetic fields, and the Faraday rotation of background radio sources as well as pulsars for our Milky Way. It is easy to get a global structure for magnetic fields in nearby galaxies, while we have observed many details of magnetic fields in our Milky Way, especially by using pulsar rotation measure data. In general, magnetic fields in spiral galaxies probably have a large-scale structure. The fields follow the spiral arms with or without the field direction reversals. In the halo of spiral galaxies magnetic fields exist and probably also have a large-scale structure as toroidal and poloidal fields, but seem to be slightly weaker than those in the disk. In the central region of some galaxies, poloidal fields have been detected as vertical components. Magnetic field directions in galaxies seem to have been preserved during cloud formation and star formation, from large-scale diffuse interstellar medium to molecular clouds and then to the cloud cores in star formation regions or clumps for the maser spots. Magnetic fields in galaxies are passive to dynamics.

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The interstellar magnetic field near the Galactic center

Ferrière¹

2009

Astron Nachr

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We review the current observational knowledge of the interstellar magnetic field within ∼150 pc of the Galactic center. We also discuss the various theoretical scenarios that have been put forward to explain the existing observations. Our critical overview leads to two important conclusions: (1) The interstellar magnetic field near the GC is approximately poloidal on average in the diffuse intercloud medium and approximately horizontal in dense interstellar clouds. (2) In the general intercloud medium, the field is relatively weak and probably close to equipartition with cosmic rays (B ∼ (6-20) µG), but there exist a number of localized filaments where the field is much stronger (some filaments could possibly have B 1 mG). In dense interstellar clouds, the field is probably rather strong, with typical values ranging between a few 0.1 mG and a few mG.

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Rotation Measures of Extragalactic Sources behind the Southern Galactic Plane: New Insights into the Large‐Scale Magnetic Field of the Inner Milky Way

Cited by 225 publications

References 30 publications

The large-scale magnetic field in the fourth Galactic quadrant

The large-scale magnetic field in the fourth Galactic quadrant

Magnetic fields in our Milky Way Galaxy and nearby galaxies

The interstellar magnetic field near the Galactic center

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