Morphological and spectral properties of the W51 region measured with the MAGIC telescopes
Morphological and spectral properties of the W51 region measured with the MAGIC telescopes
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DOI：
10.1051/0004-6361/201218846
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发表时间：
2012-01
影响因子：
6.5
通讯作者：
M. C. J. Aleksi'c;E. Alvarez;L. A. Antonelli;P. Antoranz;M. Asensio;Michael Backes;U. D. Almeida
中科院分区：
文献类型：
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作者：
M. C. J. Aleksi'c;E. Alvarez;L. A. Antonelli;P. Antoranz;M. Asensio;Michael Backes;U. D. Almeida
W51复合体是超新星遗迹W51C的所在地，已知它与恒星形成区域W51B的分子云相互作用。此外，一个可能的脉冲星风星云CXO J192318.5+140305被发现可能与超新星遗迹有关。费米/LAT(0.2到50GeV)和H.E.S.(>；1TeV)发现了这一区域的伽马射线发射。这些事件的空间分布不能用来确定脉冲星风星云、超新星残余壳和/或分子云之间的发射位置。然而，费米/LAT合作提出的光谱能量分布的模拟表明了一种强子发射机制。这类天体发出的伽马射线可能源于强子，这有助于解决超新星残留物对星系宇宙射线的贡献这一长期存在的问题。目标。我们的目标是确定W51的超高能伽马射线发射的形态并测量其光谱性质。方法：研究方法。我们用魔术望远镜对W51复合体进行了50多小时的观测，魔术的能量范围从50GeV扩展到几个TeV，允许在这些能量下进行第一次光谱测量。此外，在中等能量(几百GeV)到高能量(1TeV以上)下良好的角分辨率使我们能够进行形态研究。我们通过详细的形态研究来寻找潜在的结构。从这个源获得的多波长数据已经被采样，以模拟轻子过程和强子过程的发射。结果。我们探测到超高能伽马射线的扩展发射，其显著意义为11个标准偏差。我们将光谱从最高的Fermi/LAT能级扩展到类似于5TeV，发现它遵循指数为2.58+/-0.07(STAT)+/-0.22(SYST)的单幂定律。发射的主要部分与受冲击的云区重合，而我们发现一个特征向脉冲星风星云延伸。脉冲星风星云的可能贡献，假设是点状来源，不依赖于能量，约占总排放量的20%。宽带谱能量分布可以用一个强子模型来解释，该模型意味着质子加速超过100TeV。这一结果，连同源的形态，初步表明我们在超新星遗迹和云之间的相互作用区观察到了离子的持续加速。
The W51 complex hosts the supernova remnant W51C which is known to interact with the molecular clouds in the star forming region W51B. In addition, a possible pulsar wind nebula CXO J192318.5+140305 was found likely associated with the supernova remnant. Gamma-ray emission from this region was discovered by Fermi/LAT (between 0.2 and 50 GeV) and H. E. S. S. (>1 TeV). The spatial distribution of the events could not be used to pinpoint the location of the emission among the pulsar wind nebula, the supernova remnant shell and/or the molecular cloud. However, the modeling of the spectral energy distribution presented by the Fermi/LAT collaboration suggests a hadronic emission mechanism. The possibility that the gamma-ray emission from such an object is of hadronic origin can contribute to solvingthe long-standing problem of the contribution to galactic cosmic rays by supernova remnants. Aims. Our aim is to determine the morphology of the very-high-energy gamma-ray emission of W51 and measure its spectral properties. Methods. We performed observations of the W51 complex with the MAGIC telescopes for more than 50 h. The energy range accessible with MAGIC extends from 50 GeV to several TeV, allowing for the first spectral measurement at these energies. In addition, the good angular resolution in the medium (few hundred GeV) to high (above 1 TeV) energies allow us to perform morphological studies. We look for underlying structures by means of detailed morphological studies. Multi-wavelength data from this source have been sampled to model the emission with both leptonic and hadronic processes. Results. We detect an extended emission of very-high-energy gamma rays, with a significance of 11 standard deviations. We extend the spectrum from the highest Fermi/LAT energies to similar to 5 TeV and find that it follows a single power law with an index of 2.58 +/- 0.07(stat) +/- 0.22(syst). The main part of the emission coincides with the shocked cloud region, while we find a feature extending towards the pulsar wind nebula. The possible contribution of the pulsar wind nebula, assuming a point-like source, shows no dependence on energy and it is about 20% of the overall emission. The broad band spectral energy distribution can be explained with a hadronic model that implies proton acceleration above 100 TeV. This result, together with the morphology of the source, tentatively suggests that we observe ongoing acceleration of ions in the interaction zone between supernova remnant and cloud.