通过同步辐射发射涨落研究银河系星际湍流：首次 LOFAR 银河系前景探测
星系天体物理
2013-08-20 v2
摘要
湍流的特征外尺度和磁场随机分量与有序分量的比率是表征星际气体中磁湍流的关键参数，这影响着宇宙射线在银河系内的传播。我们为这两个参数提供了新的约束。我们利用低频阵列（LOFAR）在 [146,174] MHz 频段内，以 80"×70" 的分辨率对扇区 (l,b) (137.0,+7.0) 的弥漫连续谱发射进行成像。我们探测到了银河系同步辐射发射中的多尺度涨落并计算了其功率谱。首次应用文献中的理论估计和推导，我们从这些涨落的特征中推导出了湍流的外尺度以及随机磁场与有序磁场的比率。我们获得了迄今为止扇区最深的图像，并在主波束内发现了弥漫连续谱发射。前景同步辐射涨落的功率谱在 100 到 8 角分的尺度范围内表现出幂律行为，斜率为 (-1.84+/-0.19)。我们发现朝向扇区的星际磁湍流外尺度的上限约为 20 pc。我们还发现随机场与有序场的比率随银河系坐标变化，支持存在不同的湍流机制。我们利用来自 LOFAR 以及早期 GMRT 和 WSRT 观测的功率谱涨落来约束银河系同步辐射前景的湍流外尺度，发现 plausible 值范围为 10-20 pc。随后，我们利用这些信息推导出有序磁场强度与随机磁场强度比率的下限。对于所考虑的 LOFAR、WSRT 和 GMRT 场，这些值分别为 0.3、0.3 和 0.5。这两个约束均与之前的估计一致。
引用
@article{arxiv.1308.2804,
title = {Studying Galactic interstellar turbulence through fluctuations in synchrotron emission: First LOFAR Galactic foreground detection},
author = {M. Iacobelli and M. Haverkorn and E. Orrú and R. F. Pizzo and J. Anderson and R. Beck and M. R. Bell and A. Bonafede and K. Chyzy and R. -J. Dettmar and T. A. Enßlin and G. Heald and C. Horellou and A. Horneffer and W. Jurusik and H. Junklewitz and M. Kuniyoshi and D. D. Mulcahy and R. Paladino and W. Reich and A. Scaife and C. Sobey and C. Sotomayor-Beltran and A. Alexov and A. Asgekar and I. M. Avruch and M. E. Bell and I. van Bemmel and M. J. Bentum and G. Bernardi and P. Best and L. Birzan and F. Breitling and J. Broderick and W. N. Brouw and M. Bruggen and H. R. Butcher and B. Ciardi and J. E. Conway and F. de Gasperin and E. de Geus and S. Duscha and J. Eisloffel and D. Engels and H. Falcke and R. A. Fallows and C. Ferrari and W. Frieswijk and M. A. Garrett and J. Griessmeier and A. W. Gunst and J. P. Hamaker and T. E. Hassall and J. W. T. Hessels and M. Hoeft and J. Horandel and V. Jelic and A. Karastergiou and V. I. Kondratiev and L. V. E. Koopmans and M. Kramer and G. Kuper and J. van Leeuwen and G. Macario and G. Mann and J. P. McKean and H. Munk and M. Pandey-Pommier and A. G. Polatidis and H. Röttgering and D. Schwarz and J. Sluman and O. Smirnov and B. W. Stappers and M. Steinmetz and M. Tagger and Y. Tang and C. Tasse and C. Toribio and R. Vermeulen and C. Vocks and C. Vogt and R. J. van Weeren and M. W. Wise and O. Wucknitz and S. Yatawatta and P. Zarka and A. Zensus},
journal= {arXiv preprint arXiv:1308.2804},
year = {2013}
}
备注
13 pages, 11 figures, accepted for publication in A&A