Linear polarization structures in LOFAR observations of the interstellar medium in the 3C196 field

Abstract

This study aims to characterize linear polarization structures in LOFAR observations of the interstellar medium (ISM) in the 3C196 field, one of the primary fields of the LOFAR-Epoch of Reionization key science project. We have used the high band antennas (HBA) of LOFAR to image this region and Rotation Measure (RM) synthesis to unravel the distribution of polarized structures in Faraday depth. The brightness temperature of the detected Galactic emission is $5-15\mathrm{K}$ in polarized intensity and covers the range from -3 to +8 $\mathrm{rad}{\mathrm{m}}^{-2}$ in Faraday depth. The most interesting morphological feature is a strikingly straight filament at a Faraday depth of $+0.5\mathrm{rad}{\mathrm{m}}^{-2}$ running from north to south, right through the centre of the field and parallel to the Galactic plane. There is also an interesting system of linear depolarization canals conspicuous in an image showing the peaks of Faraday spectra. We used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. For the first time, we see some common morphology in the RM cubes made at 150 and 350~{\rm MHz}. There is no indication of diffuse emission in total intensity in the interferometric data, in line with results at higher frequencies and previous LOFAR observations. Based on our results, we determined physical parameters of the ISM and proposed a simple model that may explain the observed distribution of the intervening magneto-ionic medium. The mean line-of-sight magnetic field component, $B_{\parallel }$, is determined to be $0.3\pm 0.1\mu \mathrm{G}$ and its spatial variation across the 3C196 field is $0.1\mu \mathrm{G}$. The filamentary structure is probably an ionized filament in the ISM, located somewhere within the Local Bubble. This filamentary structure shows an excess in thermal electron density ($n_e{B}_{\parallel }>6.2\mathrm{c}{\mathrm{m}}^{-3}\mu \mathrm{G}$) compared to its surroundings.

16 pages, 10 figures, aceppted for publication in A&A

References in corpus (9)

• Radio observational constraints on Galactic 3D-emission models
• The Vertical Structure of Warm Ionised Gas in the Milky Way
• Post-correlation radio frequency interference classification methods
• All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz
• Characterizing Foreground for redshifted 21-cm radiation: 150 MHz GMRT observations
• The LOFAR radio environment
• Initial LOFAR observations of Epoch of Reionization windows: II. Diffuse polarized emission in the ELAIS-N1 field
• Galactic interstellar filaments as probed by LOFAR and Planck
• Adaptive Weighting in Radio Interferometric Imaging

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