Metal-rich multi-phase gas in M 87 - AGN-driven metal transport, magnetic-field supported multi-temperature gas, and constraints on non-thermal emission observed with XMM-Newton
Metal-rich multi-phase gas in M 87 - AGN-driven metal transport, magnetic-field supported multi-temperature gas, and constraints on non-thermal emission observed with XMM-Newton
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DOI：
10.1051/0004-6361:20078749
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发表时间：
2007-09
影响因子：
6.5
通讯作者：
A. Simionescu;N. Werner;A. Finoguenov;H. Böhringer;M. Brüggen
中科院分区：
文献类型：
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作者：
A. Simionescu;N. Werner;A. Finoguenov;H. Böhringer;M. Brüggen
我们利用M87晕的深(∼，120k)xMM-牛顿数据分析了它的空间分辨温度结构和化学成分。我们特别关注与内部射电叶相关的X射线亮度增强的区域，这些区域已知不能用单温度谱模型很好地描述。与简单的双温度拟合相比，我们使用一个包含每个空间面元内连续温度范围的模型来更好地、更物理地描述光谱。多相气体的温度范围为∼0.6-3.2keV。只有在磁场抑制热传导的情况下，这种多相结构才有可能。在多温区，我们发现冷气体的量(温度低于周围X射线等离子体的温度)与金属丰度之间存在关联，得出冷气体比周围晕更富金属的结论。在假设的热模型框架下，我们估算了∼2.2太阳冷气体的平均Fe丰度。因此，我们的结果指出，活动星系核(AGN)通过从星系中抬起冷的、富金属的气体，将重元素输送到星系团内介质中，发挥了关键作用。然而，X线臂内外的O/Si/S/Fe丰度比相似，表明气体晕中的主要金属组分是在较晚的活动星系核爆发中抬升的，而不是M87岁。我们对冷却气体质量的最佳估计是5×108M�，它可能来自于冰河、恒星质量损失和Ia型超新星产品的混合。需要≈30-110Myr才能在冷气体中产生观察到的金属。最后，我们给出了M87可能的非热X射线发射的上限，并结合90厘米射电地图，我们给出了磁场强度的下限，约为∼0.51.0uG。
We use deep (∼120 ks) XMM-Newton data of the M 87 halo to analyze its spatially resolved temperature structure and chemical composition. We focus particularly on the regions of enhanced X-ray brightness associated with the inner radio lobes, which are known not to be described very well by single-temperature spectral models. Compared to a simple two-temperature fit, we obtain a better and more physical description of the spectra using a model that involves a continuous range of temperatures in each spatial bin. The range of temperatures of the multiphase gas spans ∼0.6–3.2 keV. Such a multiphase structure is only possible if thermal conduction is suppressed by magnetic fields. In the multi-temperature regions, we find a correlation between the amount of cool gas (with a temperature below that of the surrounding X-ray plasma) and the metallicity, and conclude that the cool gas is more metalrich than the ambient halo. In the frame of the assumed thermal model, we estimate the average Fe abundance of the cool gas to ∼2.2 solar. Our results thus point toward the key role of the active galactic nucleus (AGN) in transporting heavy elements into the intracluster medium through the uplift of cool, metal-rich gas from the galaxy. However, the abundance ratios of O/Si/S/Fe in and outside the X-ray arms are similar, indicating that the dominant fraction of metals in the gas halo was uplifted by AGN outbursts relatively recently compared to the age of M 87. Our best estimate for the mass of the cool gas is 5 × 10 8 M� , which probably stems from a mixture of ICM, stellar mass loss, and Type Ia supernova products. ≈30–110 Myr are required to produce the observed metals in the cool gas. Finally, we put upper limits on possible non-thermal X-ray emission from M 87 and, combining it with the 90 cm radio maps, we put lower limits of around ∼0.5–1.0 µG on the magnetic field strength.