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arXiv 0801.4803astro-ph
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SNR S147的射电频谱特性和磁场

Radio spectral properties and the magnetic field of the SNR S147

L. Xiao, E. Fürst, W. Reich, J. L. Han

摘要:

S147是一个巨大的暗壳型超新星遗迹(SNR)。它在厘米波长处的显著光谱突变是表征信噪比演化的重要物理性质。然而,频谱中断是基于精确度有限的射电观测。我们用Effelsberg 100米望远镜和乌鲁木齐25米望远镜分别在11厘米和6厘米波段对S147进行了新的射电连续谱和偏振观测。这些新的数据与发表的低频率数据从Effelsberg 100米望远镜和甚高频数据从WMAP调查光谱周转和偏振特性的S147。S147由许多嵌入在漫发射中的细丝组成。在11 cm和6cm处的积分通量密度分别为34.8 ± 4.0Jy和15.4 ± 3.0Jy。这些新的测量结果证实了在~1.5GHz处的已知光谱转换,这可以完全归因于漫发射分量。成交量上方的光谱指数为-1.35+/-0.20。附加发射分量在高达40.7GHz的整个波长范围内具有恒定的光谱指数,为-0.35+/-0.15。S147的弱偏振辐射与周围的银河系漫射偏振处于同一水平。东半球壳的自转量约为-70 rad/m2。S147的散射发射和散射发射具有不同的物理性质,这使得S147在壳型信噪比中表现突出,S147在11 cm和6 cm处的弱极化可以归因于S147壳层的一个切向磁场方向。

英文摘要:

(Abridged) S147 is a large faint shell-type supernova remnant (SNR). Its remarkable spectral break at cm-wavelengths is an important physical property to characterize the SNR evolution. However, the spectral break is based on radio observations with limited precision. We made new radio continuum and polarization observations of S147 at 11cm and at 6cm with the Effelsberg 100-m telescope and the Urumqi 25-m telescope, respectively. These new data were combined with published lower frequency data from the Effelsberg 100-m telescope and very high frequency data from WMAP to investigate the spectral turnover and polarization properties of S147. S147 consists of numerous filaments embedded in diffuse emission. We found that the integrated flux densities of S147 are 34.8+/-4.0 Jy at 11cm and 15.4+/-3.0Jy at 6cm. These new measurements confirm the known spectral turnover at ~1.5GHz, which can be entirely attributed to the diffuse emission component. The spectral index above the turnover is -1.35+/-0.20. The filamentary emission component has a constant spectral index over the entire wavelength range up to 40.7GHz of -0.35+/-0.15. The weak polarized emission of S147 is at the same level as the ambient diffuse Galactic polarization. The rotation measure of the eastern filamentary shell is about -70 rad/m2. The filamentary and diffuse emission components of S147 have different physical properties, which make S147 outstanding among shell type SNRs.The weak polarization of S147 at 11cm and at 6cm can be attributed to a section of the S147 shell showing a tangential magnetic field direction.

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