X. H. Sun

A Sino-German λ6 cm polarization survey of the Galactic plane - V. Large supernova remnants

Context. Observations of large supernova remnants (SNRs) at high frequencies are rare, but provide valuable information about their physical properties. Aims. The total intensity and polarization properties of 16 large SNRs in the Galactic p lane are investigated based on observations of the Urumqi¸ 6 cm polarization survey of the Galactic plane with an angular resolution of 9: 5. Methods. We extracted total intensity and linear polarization maps of large SNRs from the Urumqi¸ 6 cm survey, obtained their integrated flux densities, and derived the radio spectra by using these flu x densities together with previously published flux densities at various frequencies. In particular, Effelsberg¸ 11 cm and¸ 21 cm survey data were used to calculate integrated flux densities. The ¸ 6 cm polarization data also delineate the magnetic field structures of the SNRs. Results. We present the first total intensity maps at ¸ 6 cm for SNRs G106.3+2.7, G114.3+0.3, G116.5+1.1, G166.0+4.3 (VRO 42.05.01), G205.5+0.5 (Monoceros Nebula), and G206.9+2.3 (PKS 0646+06) and the first polarization measurements at ¸ 6 cm for SNRs G82.2+5.3 (W63), G106.3+2.7, G114.3+0.3, G116.5+1.1, G166.0+4.3 (VRO 42.05.01), G205.5+0.5 (Monoceros Nebula), and G206.9+2.3 (PKS 0646+06). Most of the newly derived integrated radio spectra are consistent with previous results. The new flux densities obtained from the Urumqi ¸ 6 cm, Effelsberg¸ 11 cm and¸ 21 cm surveys are crucial to determine the spectra of SNR G65.1+0.6, G69.0+2.7 (CTB 80), G93.7-0.2, and G114.3+0.3. We find that G192.8i 1.1 (PKS 0607+17) consists of background sources, H II regions, and extended diffuse emission of thermal nature, and conclude that G192.8i 1.1 is not a SNR.

A Sino-German λ6 cm polarization survey of the Galactic plane - VII. Small supernova remnants

We study the spectral and polarization properties of supernova remnants (SNRs) based on our 6cm survey data. The observations were taken from the Sino-German 6cm polarization survey of the Galactic plane. By using the integrated flux densities at 6cm together with measurements at other wavelengths from the literature we derive the global spectra of 50 SNRs. In addition, we use the observations at 6cm to present the polarization images of 24 SNRs. We derived integrated flux densities at 6cm for 51 small SNRs with angular sizes less than 1 degree. Global radio spectral indices were obtained in all the cases except for Cas A. For SNRs G15.1-1.6, G16.2-2.7, G16.4-0.5, G17.4-2.3, G17.8-2.6, G20.4+0.1, G36.6+2.6, G43.9+1.6, G53.6-2.2, G55.7+3.4, G59.8+1.2, G68.6-1.2, and G113.0+0.2, the spectra have been significantly improved. From our analysis we argue that the object G16.8-1.1 is probably an HII region instead of a SNR. Cas A shows a secular decrease in total intensity, and we measured a flux density of 688+/-35 Jy at 6cm between 2004 and 2008. Polarized emission from 25 SNRs were detected. For G16.2-2.7, G69.7+1.0, G84.2-0.8 and G85.9-0.6, the polarized emission is detected for the first time confirming them as SNRs. High frequency observations of SNRs are rare but important to establish their spectra and trace them in polarization in particular towards the inner Galaxy where Faraday effects are important.

A Sino-German λ6 cm polarization survey of the Galactic plane - II. The region from 129° to 230° longitude

Context. Linearly polarized Galactic synchrotron emission provides valuable information about the properties of the Galactic magnetic field and the interstellar magneto-ionic medium, when Faraday rotation a long the line of sight is properly taken into account. Aims. We aim to survey the Galactic plane atλ6 cm including linear polarization. At such a short wavelength Faraday rotation effects are in general small and the Galactic magnetic field properties can be prob ed to larger distances than at long wavelengths. Methods. The Urumqi 25-m telescope is used for a sensitive λ6 cm survey in total and polarized intensities. WMAP K-band (22.8 GHz) polarization data are used to restore the absolute zero-level of the Urumqi U and Q maps by extrapolation. Results. Total intensity and polarization maps are presented for a Galactic plane reg ion of 129 ◦ ≤ l ≤ 230 ◦ and|b| ≤ 5 ◦ in the anti-centre with an angular resolution of 9. 5 and an average sensitivity of 0.6 mK and 0.4 mK TB in total and polarized intensity, respectively. We briefly discuss the properties of some extended Fara day Screens detected in theλ6 cm polarization maps. Conclusions. The Sino-Germanλ6 cm polarization survey provides new information about the properties of the magnetic ISM. The survey also adds valuable information for discrete Galactic objects and is in particular suited to detect extended Faraday Screens with large rotation measures hosting strong regular magnetic fields.

A Sino-German λ6 cm polarization survey of the Galactic plane - III. The region from 10° to 60° longitude

Aims. We aim to study polarized short-wavelength emission from the inner Galaxy, which is nearly invisible at long wavelengths because of depolarization. Information on the diffuse continuum emission at short wavelengths is required to separate Galactic thermal and non-thermal components including existing long-wavelength data. Methods. We have conducted a total intensity and polarization survey of the Galactic plane at �6 cm using the Urumqi 25 m telescope for the Galactic longitude range of 10 � �l�60 � and the Galactic latitude range ofj bj� 5 � . Missing absolute zero levels of Stokes U and Q maps were restored by extrapolating the WMAP five-year K-ban d polarization data. For total intensities we recovered mis sing large-scale components by referring to the Effelsberg �11 cm survey. Results. Total intensity and polarization maps are presented with an angular resolution of 9. 5 and a sensitivity of 1 mK TB and 0.5 mK TB in total and polarized intensity, respectively. The �6 cm polarized emission in the Galactic plane originates within about 4 kpc distance, which increases for polarized emission out of the plane. The polarization map shows “patches”, “canals” and “voids” with no correspondence in total intensity. We attribute the patches to turbulent magnetic field cells. Canals are caused by abrupt variation of polarization angles at the boundaries of patches ra ther than by foreground Faraday Screens. The superposition of foreground and Faraday Screen rotated background emission almost cancels polarized emission locally, so that polarization voids appear. By modelling the voids, we estimate the Faraday Screen’s regul ar magnetic field along the line-of-sight to be larger than ab out 8 µG. We separated thermal (free-free) and non-thermal (synchrotron) emission according to their different spectral indices. The spectral index for the synchrotron emission was based on WMAP polarization data. The fraction of thermal emission at �6 cm is about 60% in the plane. Conclusions. The Sino-German�6 cm polarization survey of the inner Galaxy provides new insights into the properties of the magnetized interstellar medium for this very complex Galactic region, which is Faraday thin up to about 4 kpc in the Galactic plane. Within this distance polarized patches were identified as in trinsic structures related to turbulent Galactic magnetic fields for spatial scales from 20(d/4 kpc) to 200(d/4 kpc) pc

A Sino-German λ6 cm polarization survey of the Galactic plane - VI. Discovery of supernova remnants G178.2−4.2 and G25.1−2.3

Supernova remnants (SNRs) were often discovered in radio surveys of the Galactic plane. Because of the surface-brightness limit of previous surveys, more faint or confused SNRs await discovery. The Sino-German

New λ6 cm and λ11 cm observations of the supernova remnant CTA 1

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Giant Lobes of Centaurus A as Seen in Radio and Gamma-Ray Images Obtained with the Fermi-LAT and Planck Satellites

6\ cm Galactic plane survey is a sensitive survey with the potential to detect new low surface-brightness SNRs. We want to identify new SNRs from the

Energy distribution of relativistic electrons in the young supernova remnant G1.9+0.3

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Energy distribution of relativistic electrons in the kiloparsec scale jet of M 87 with Chandra

6\ cm survey map of the Galactic plane. We searched for new shell-like objects in the

Giant lobes of Centaurus A as seen in radio and γ-ray images obtained with the Fermi-LAT and Planck satellites

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