A Sino-German<i>λ</i>6 cm polarization survey of the Galactic plane

Gao, Xiaoqing; Han, J. L.; Reich, W.; Reich, P.; Wielebinski, R.

doi:10.1051/0004-6361/201016311

Cited by 82 publications

(108 citation statements)

References 97 publications

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“…The spectral index of the SNR G206.9+2.3 presents fairly uniform distribution and has an averaged index of β = −2.46, similar to the value found for its integrated flux densities by Gao et al (2011). Spectral index values are generally about −0.4 in the Monoceros SNR shell region.…”

Section: Spectral Index Mapsupporting

confidence: 49%

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Radio perspectives on the Monoceros SNR G205.5+0.5

Xiao

Zhu

2012

A&A

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Context. The Monoceros supernova remnant (SNR G205.5+0.5) is a large shell-type SNR located in the Rosette molecular complex and thought to be interacting with the Rosette Nebula. Aims. We aim to re-examine the radio spectral index and its spatial variation over the Monoceros SNR as well as study its properties of evolution within the complex interstellar medium. Methods. We extracted radio continuum data for the Monoceros complex region from the Effelsberg 21 cm and 11 cm surveys and the Urumqi 6 cm polarization survey. We used the new Arecibo GALFA-HI survey data with much higher resolution and sensitivity than that previously available to identify the HI shell related with the SNR. Multi-wavelengths data are included to investigate the properties of the SNR. Results. The spectral index α (S ν ∝ ν α ) averaged over the SNR is −0.41 ± 0.16. The TT-plots and the distribution of α over the SNR show spatial variations that steepen toward the inner western filamentary shell. Polarized emission is prominent on the western filamentary shell region. The RM there is estimated to be about 30 ± 77n rad m −2 , where the n = 1 solution is preferred, and the magnetic field has a strength of about 9.5 μG. From the HI channel maps, further evidence is provided for an interaction between the Monoceros SNR and the Rosette Nebula. We identify partial neutral hydrogen shell structures in the northwestern region at velocities of +15 km s −1 circumscribing the continuum emission. The HI shell has swept up a mass of about 4000 M for a distance of 1.6 kpc. The western HI shell, well associated with the dust emission, is found to lie outside of the radio shell. We suggest that the Monoceros SNR is evolving within a cavity blown out by the progenitor and has triggered part of the star formation in the Rosette Nebula. Conclusions. The Monoceros SNR is interacting with the ambient interstellar medium with ultra-high energy emission detected. Its interaction with the Rosette Nebula is further supported by new evidence from HI data, which will help the investigation of the emission mechanism of the high-energy emission.

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Section: Spectral Index Mapsupporting

confidence: 49%

“…35+1.35) in the eastern periphery from its thermal spectrum. Gao et al (2011) showed a new polarization observation at 4800 MHz. Combining this observation with Effelsberg 21 cm and 11 cm data, they obtained a spectral index of α = −0.43 ± 0.12 for the western shell.…”

Section: Introductionmentioning

confidence: 99%

Radio perspectives on the Monoceros SNR G205.5+0.5

Xiao

Zhu

2012

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“…In this paper, we present new λ6 cm and λ11 cm observations of CTA 1, which is one of the targets of a campaign to map large northern sky SNRs at λ6 cm. This project is part of the Sino-German λ6 cm polarisation survey of the Galactic plane Gao et al 2010;Sun et al 2011;Xiao et al 2011;Gao et al 2011). Results on some large SNRs have been already reported, such as G65.2+5.7 (Xiao et al 2009), the Cygnus Loop (Sun et al 2006), HB 3 (Shi et al 2008), G156.2+5.7 (Xu et al 2007), and S 147 (Xiao et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Newλ6 cm andλ11 cm observations of the supernova remnant CTA 1

Sun

Reich

Wang

et al. 2011

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Aims. We attempt to study spatial variations in the spectrum and rotation measures (RMs) of the large-diameter, high-latitude supernova remnant (SNR) CTA 1. Methods. We conducted new λ6 cm and λ11 cm observations of CTA 1 using the Urumqi 25-m and Effelsberg 100-m telescopes. Data at other wavelengths were included to investigate the spectrum and polarisation properties. Results. We obtained new total intensity and polarisation maps at λ6 cm and λ11 cm with angular resolutions of 9. 5 and 4. 4, respectively. We derived a spectral index of α = −0.63 ± 0.05 (S ν ∝ ν α ) based on the integrated flux densities at 408 MHz, 1420 MHz, 2639 MHz, and 4800 MHz. The spectral index map calculated from data at the four frequencies shows a clear steepening of the spectrum from the strong shell emission towards the north-western breakout region with weak diffuse emission. The decrease of the spectral index is up to about Δα = 0.3. The RM map derived from polarisation data at λ6 cm and λ11 cm shows a sharp transition between positive RMs in the north-eastern and negative RMs in the south-western part of the SNR. We note a corresponding RM pattern of extragalactic sources and propose the existence of a large-diameter Faraday screen in front of CTA 1, which covers the north-eastern part of the SNR. The RM of the Faraday screen is estimated to be about +45 rad m −2 . A RM structure function of CTA 1 indicates a very regular magnetic field within the Faraday screen, which is stronger than about 2.7 μG for a distance of 500 pc. Conclusions. CTA 1 is a large-diameter shell-type SNR located out of the Galactic plane, which makes it an ideal object to study its properties without suffering confusion. The previous detection of the rare breakout phenomenon in CTA 1 is confirmed. We identify a Faraday screen partly covering CTA 1 with a regular magnetic field in the opposite direction to the interstellar magnetic field. The detection of Faraday screens in the Galactic plane is quite common, but is difficult at high latitudes where the polarisation angles of weak polarised background emission are rotated. Additional RMs from extragalactic sources are needed for this purpose, although the number density of the extragalactic RMs that have been measured remains small despite significant observational progress.

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“…Many SNRs have been detected as strong discrete sources in the survey. A study of large SNRs with angular sizes exceeding about 1 • was presented by Gao et al (2011). In this paper, we focus on SNRs with a smaller angular size.…”

Section: Introductionmentioning

confidence: 99%

A Sino-Germanλ6 cm polarization survey of the Galactic plane

Sun

Reich

et al. 2011

A&A

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Aims. We study the spectral and polarization properties of supernova remnants (SNRs) using our λ6 cm survey data. Methods. We analyse data from observations taken as part of the Sino-German λ6 cm polarization survey of the Galactic plane. By using the integrated flux densities at λ6 cm together with measurements at other wavelengths from the literature, we derive the global spectra of 50 SNRs. In addition, from the observations at λ6 cm we obtain the polarization images of 24 SNRs. Results. We derive integrated flux densities at λ6 cm for 51 small SNRs with angular sizes smaller than 1 • . We are able to derive global radio spectral indices in all the cases except for Cas A. For the 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 H ii region instead of a SNR. Cas A shows a secular decrease in total intensity, and we measure a flux density of 688 ± 35 Jy at λ6 cm between 2004 and 2008. We detect polarized emission from 25 SNRs. 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 that they are SNRs. Conclusions. High-frequency observations of SNRs are difficult but essential to determine their spectra and measure their polarization in particular towards the inner Galaxy, where Faraday effects are important.

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A Sino-Germanλ6 cm polarization survey of the Galactic plane

Cited by 82 publications

References 97 publications

Radio perspectives on the Monoceros SNR G205.5+0.5

Radio perspectives on the Monoceros SNR G205.5+0.5

Newλ6 cm andλ11 cm observations of the supernova remnant CTA 1

A Sino-Germanλ6 cm polarization survey of the Galactic plane

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