POLARIMETRY AND THE HIGH-ENERGY EMISSION MECHANISMS IN QUASAR JETS: THE CASE OF PKS 1136−135
POLARIMETRY AND THE HIGH-ENERGY EMISSION MECHANISMS IN QUASAR JETS: THE CASE OF PKS 1136−135
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DOI：
10.1088/0004-637x/773/2/186
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发表时间：
2013-05
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通讯作者：
M. Cara;E. Perlman;Y. Uchiyama;C. Cheung;P. Coppi;M. Georganopoulos;D. Worrall;M. Birkinshaw;W. Sparks;H. Marshall;L. Stawarz;M. Begelman;C. O’Dea;S. Baum
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作者：
M. Cara;E. Perlman;Y. Uchiyama;C. Cheung;P. Coppi;M. Georganopoulos;D. Worrall;M. Birkinshaw;W. Sparks;H. Marshall;L. Stawarz;M. Begelman;C. O’Dea;S. Baum
自从发现类星体喷流发出千秒差距尺度的 X 射线以来，导致其高能发射的物理过程一直没有明确的定义。许多机制正在激烈争论，包括同步加速器辐射、逆康普顿化宇宙微波背景（IC/CMB）发射和其他康普顿化过程。在许多情况下，射流区域的光学和 X 射线发射由单个光谱成分标记，在这些情况下，可以将高分辨率多波段成像和偏振测量相结合，以对射流发射过程进行强大的诊断。在这里，我们报告了用哈勃太空望远镜获得的 PKS 1136−135 射流的深度成像光度测量。我们发现几个结在光学上是高度偏振的，分数偏振 Π > 30%。当与在这些区域观察到的宽带光谱形状相结合时，这很难通过 IC/CMB 模型来解释，除非散射粒子位于电子能量分布的最低能量尖端，洛伦兹因子 γ ~ 1，并且射流也具有非常高的光束（δ ⩾ 20）并且在视线的几度范围内观察到。我们根据这一新证据讨论了 X 射线发射的 IC/CMB 和同步加速器解释，提出了光谱能量分布以及该射流的物质含量的新模型。高偏振并不能完全排除该射流中 IC/CMB 光学到 X 射线发射的可能性，但它们确实强烈不利于该模型。我们讨论了这一发现的含义，以及未来工作的前景。
Since the discovery of kiloparsec-scale X-ray emission from quasar jets, the physical processes responsible for their high-energy emission have been poorly defined. A number of mechanisms are under active debate, including synchrotron radiation, inverse-Comptonized cosmic microwave background (IC/CMB) emission, and other Comptonization processes. In a number of cases, the optical and X-ray emission of jet regions are inked by a single spectral component, and in those, high-resolution multi-band imaging and polarimetry can be combined to yield a powerful diagnostic of jet emission processes. Here we report on deep imaging photometry of the jet of PKS 1136−135 obtained with the Hubble Space Telescope. We find that several knots are highly polarized in the optical, with fractional polarization Π > 30%. When combined with the broadband spectral shape observed in these regions, this is very difficult to explain via IC/CMB models, unless the scattering particles are at the lowest-energy tip of the electron energy distribution, with Lorentz factor γ ∼ 1, and the jet is also very highly beamed (δ ⩾ 20) and viewed within a few degrees of the line of sight. We discuss both the IC/CMB and synchrotron interpretation of the X-ray emission in the light of this new evidence, presenting new models of the spectral energy distribution and also the matter content of this jet. The high polarizations do not completely rule out the possibility of IC/CMB optical-to-X-ray emission in this jet, but they do strongly disfavor the model. We discuss the implications of this finding, and also the prospects for future work.