Catalogue of unambiguous (Faraday-thin, one-component, spectrum-selected) rotation measures for galaxies and quasars

Broten, N. W.; MacLeod, J. M.; Vallée, J. P.

doi:10.1007/bf00639497

Cited by 67 publications

(71 citation statements)

References 7 publications

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“…The Galactic foreground RM in this general direction is known to be quite extreme (cf. Broten et al 1988;Han & Qiao 1994), even at tens of degrees from the Galactic plane. The brighter lobes of two resolved double sources in the field suggest a value of about −177 ± 7 rad m −2 .…”

Section: Ngc 4826 (M64)mentioning

confidence: 99%

The Westerbork SINGS survey

Heald¹,

Braun

Edmonds

2009

A&A

211

292

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A sample of large northern Spitzer Infrared Nearby Galaxies Survey (SINGS) galaxies has recently been observed with the Westerbork Synthesis Radio Telescope (WSRT). We present observations of the linearly polarized radio continuum emission in this WSRT-SINGS galaxy sample. Of the 28 galaxies treated in this paper, 21 are detected in polarized radio continuum at 18-and 22-cm wavelengths. We utilize the rotation measure synthesis (RM-Synthesis) method, as implemented by Brentjens & de Bruyn (2005, A&A, 441, 1217, to coherently detect polarized emission from a large fractional bandwidth, while simultaneously assessing the degree of Faraday rotation experienced by the radiation along each line-of-sight. This represents the first time that the polarized emission and its Faraday rotation have been systematically probed down to ∼10 μJy beam −1 RMs for a large sample of galaxies. Non-zero Faraday rotation is found to be ubiquitous in all of the target fields, from both the Galactic foreground and the target galaxies themselves. In this paper, we present an overview of the polarized emission detected in each of the WSRT-SINGS galaxies. The most prominent trend is a systematic modulation of the polarized intensity with galactic azimuth, such that a global minimum in the polarized intensity is seen toward the kinematically receding major axis. The implied large-scale magnetic field geometry is discussed in a companion paper. A second novel result is the detection of multiple nuclear Faraday depth components that are offset to both positive and negative RM by 100−200 rad m −2 in all targets that host polarized (circum-)nuclear emission.

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Section: Ngc 4826 (M64)mentioning

confidence: 99%

The Westerbork SINGS survey

Heald¹,

Braun

Edmonds

2009

A&A

211

292

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“…We constrain the model using RM data from individual sources only within the SGPS region (120 pulsars, 148 SGPS EGSs, and 1 EGS from Broten et al [1988]; see xx 2 and 3). 10 For modeling purposes, we assume that the intergalactic contribution to the EGS RMs is negligible (Simard-Normandin & Kronberg 1980;Gaensler et al 2005), so that the EGSs may be considered to reside at Galactocentric radii of 20 kpc.…”

Section: Modeling the Large-scale Magnetic Fieldmentioning

confidence: 99%

“…RMs at these longitudes nominally should be dominated by the field in the , so that sources with jRMj < 100 rad m À2 are set to 100 rad m À2 , and those with jRMj > 600 rad m À2 are set to 600 rad m À2 . In the top panel, the square at l ¼ 307:1 , b ¼ 1:2 represents the EGS RM previously observed by Broten et al (1988), while the squares at l $ 330 represent the EGS RMs of the SGPS test region. The circles in the top panel represent the SGPS EGSs as given in Table 1.…”

Section: Modeling the Large-scale Magnetic Fieldmentioning

confidence: 99%

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

Brown

Haverkorn

Gaensler

et al. 2007

ApJ

225

287

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We present new Faraday rotation measures ( RMs) for 148 extragalactic radio sources behind the southern Galactic plane (253 l 356 , jbj 1:5 ), and use these data in combination with published data to probe the large-scale structure of the Milky Way's magnetic field. We show that the magnitudes of these RMs oscillate with longitude in a manner that correlates with the locations of the Galactic spiral arms. The observed pattern in RMs requires the presence of at least one large-scale magnetic reversal in the fourth Galactic quadrant, located between the SagittariusCarina and Scutum-Crux spiral arms. To quantitatively compare our measurements to other recent studies, we consider all available extragalactic and pulsar RMs in the region we have surveyed, and jointly fit these data to simple models in which the large-scale field follows the spiral arms. In the best-fitting model, the magnetic field in the fourth Galactic quadrant is directed clockwise in the Sagittarius-Carina spiral arm (as viewed from the north Galactic pole), but is oriented counterclockwise in the Scutum-Crux arm. This contrasts with recent analyses of pulsar RMs alone, in which the fourth-quadrant field was presumed to be directed counterclockwise in the Sagittarius-Carina arm. Also in contrast to recent pulsar RM studies, our joint modeling of pulsar and extragalactic RMs demonstrates that large numbers of large-scale magnetic field reversals are not required to account for observations.

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“…• 5 to which we added 12 sources from Gaensler et al (2001), one from Broten et al (1988), and one from Clegg et al (1992) in the same longitude range but with 1.…”

Section: The Datamentioning

confidence: 99%

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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Catalogue of unambiguous (Faraday-thin, one-component, spectrum-selected) rotation measures for galaxies and quasars

Cited by 67 publications

References 7 publications

The Westerbork SINGS survey

The Westerbork SINGS survey

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

The large-scale magnetic field in the fourth Galactic quadrant

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