Probing the Magnetized Interstellar Medium Surrounding the Planetary Nebula Sh 2‐216

Reid³

et al. 2010

A&A

Self Cite

111

Context. Observations of polarized emission are a significant source of information on the magnetic field that pervades the interstellar medium of the Galaxy. Despite the acknowledged importance of magnetic fields in interstellar processes, our knowledge of field configurations on all scales is seriously limited. Aims. This paper describes an extensive survey of polarized Galactic emission at 1.4 GHz that provides data with arcminute resolution and complete coverage of all structures from the broadest angular scales to the resolution limit, giving information on the magnetoionic medium over a wide range of interstellar environments. • 5. This is the first extensive polarization survey to present aperture-synthesis data combined with data from single antennas, and the techniques developed to achieve this combination are described. Results. The appearance of the extended polarized emission at 1.4 GHz is dominated by Faraday rotation along the propagation path, and the diffuse polarized sky bears little resemblance to the total-intensity sky. There is extensive depolarization, arising from vector averaging on long lines of sight, from H ii regions, and from diffuse ionized gas seen in Hα images. Preliminary interpretation is presented of selected polarization features on scales from parsecs (the planetary nebula Sh 2-216) to hundreds of parsecs (a superbubble GSH 166−01−17), to kiloparsecs (polarized emission in the direction of Cygnus X).

Section: The Planetary Nebula Sharpless 2-216mentioning

confidence: 99%

A Survey of the polarized emission from the Galactic plane at 1420 MHz with arcminute angular resolution

Landecker¹,

Reid³

et al. 2010

A&A

Self Cite

111

“…The only direct observational evidence for the role of IMF in shaping IPNe was given by Ransom et al (2008). Using the estimate of the rotation measure and the electron density in the shell of S216 nebula, they derived a line-of-sight magnetic field in the interaction region of 5.0 ± 2.0 μG.…”

Section: The Galactic Orientation Of Ipnementioning

confidence: 99%

Interacting planetary nebulae

Ali

Sabin

Snaid

et al. 2012

A&A

We discuss the classification and orientation of planetary nebulae that interact with the interstellar medium throughout the Milky Way. A sample of 117 confirmed interacting planetary nebulae is used for this purpose. Our results indicate that the majority of interacting objects are located close to the Galactic plane, and ∼77% of them are located inside the Galactic thin disk. One third of the sample is less than 100 parsec from the Galactic plane and thus may interact with molecular and cold neutral clouds. There is a tendency for the planetary nebula interaction region to be parallel to the Galactic plane. We found that ∼73% of interacting planetary nebulae have inclination angles (defined as the angles that join the planetary nebula centroid and the interaction area or bow shock with the Galactic plane) larger than 45 • and ∼38% larger than 70 • , which highlights the possible effect of interstellar magnetic fields. While it is sometime believed that the interaction preferentially occurs in old planetary nebulae, our analysis indicates that the majority of observed planetary nebulae are in the mid stage of their evolution. The mean inclination angle, Galactic height, linear size, and dynamical age are estimated for each stage of interaction. The results indicate strong correlations between the mean inclination angle and the above parameters.

“…The object might be similar to the planetary nebula Sh 2−216 discussed by Ransom et al (2008) and might act as a Faraday screen in the same way as described for H ii regions above. Because its distance is small, a large fraction of the polarised Galactic emission is located behind PK050+31 and gets rotated.…”

Section: Identificationmentioning

confidence: 94%

A Sino-Germanλ6 cm polarisation survey of the Galactic plane

Sun

et al. 2013

A&A

Aims. Information of small-diameter sources is extracted from the Sino-German λ6 cm polarisation survey of the Galactic plane carried out with the Urumqi 25-m telescope. Methods. We performed two-dimensional elliptical Gaussian fits to the λ6 cm maps to obtain a list of sources with total-intensity and polarised flux densities. Results. The source list contains 3832 sources with a fitted diameter smaller than 16 and a peak flux density exceeding 30 mJy, so about 5× the rms noise, of the total-intensity data. The cumulative source count indicates completeness for flux densities exceeding about 60 mJy. We identify 125 linearly polarised sources at λ6 cm with a peak polarisation flux density greater than 10 mJy, so about 3× the rms noise of the polarised-intensity data. Conclusions. Despite lacking compact steep spectrum sources, the λ6 cm catalogue lists about 20% more sources than the Effelsberg λ21 cm source catalogue at the same angular resolution and for the same area. Most of the faint λ6 cm sources must have a flat spectrum and are either H ii regions or extragalactic. When compared with the Green Bank λ6 cm (GB6) catalogue, we obtain higher flux densities for a number of extended sources with complex structures. Polarised λ6 cm sources density are uniformly distributed in Galactic latitude. Their number density decreases towards the inner Galaxy. More than 80% of the polarised sources are most likely extragalactic. With a few exceptions, the sources have a higher percentage polarisation at λ6 cm than at λ21 cm. Depolarisation seems to occur mostly within the sources with a minor contribution from the Galactic foreground emission.