The Westerbork SINGS survey - II Polarization, Faraday rotation, and magnetic fields

By G. Heald, R. Braun, R. University, D. O. Astronomy. 2009

184 citations recorded by the source corpus.

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 μ Jy 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.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3f898fa18ec8456681beeb8115d4414b536d2c69

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Citations in the corpus

LOFAR: The LOw-Frequency ARray (2013, unknown): “Indeed this technique is now becoming standard not only for recovering widespread polarized emission in a variety of environments but also for characterizing the line of sight medium itself (e.g., de Bruyn & Brentjens 2005; Heald et al. 2009).”
Magnetic fields and spiral arms in the galaxy M51 (2010, methodology): “Heald et al. (2009) derived rotation measure maps from multichannel WSRT data at λ22 cm using the RM-synthesis technique that qualitatively show the pattern expected from a m = 1 magnetic field.”
Estimating extragalactic Faraday rotation (2014, background): “The ‘complement’ number di ﬀ ers signiﬁcantly, indicating that the assumptions made for the VIP category of data points are probably not met by all of the data points in the O’Sullivan, Heald, and Schnitzeler catalogs.”