The Origin of the X-Ray Emission in Two Well-aligned Extragalactic Jets: The Case for IC/CMB
The Origin of the X-Ray Emission in Two Well-aligned Extragalactic Jets: The Case for IC/CMB
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DOI：
10.3847/2041-8213/ab3db3
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发表时间：
2019-08
期刊：
影响因子：
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通讯作者：
E. Meyer;Adurshsiva R. Iyer;Karthik Reddy;M. Georganopoulos;Peter Breiding;M. Keenan
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文献类型：
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作者：
E. Meyer;Adurshsiva R. Iyer;Karthik Reddy;M. Georganopoulos;Peter Breiding;M. Keenan
在过去的二十年里，对于解析类星体喷流中的高强度和硬X射线发射，最常用的解释是宇宙微波背景的逆康普顿上散射（IC/CMB），这需要喷流在10-1000 kpc尺度上保持高度相对论性。近年来，各种各样的观测证据，包括伽马射线的上限，都不支持这种解释，而支持同步加速器的起源。虽然IC/CMB模型通常预测高水平的伽马射线发射，但从未被检测到。在这里，我们报告的低状态费米/LAT伽马射线光谱的检测与两个喷射的活动星系核，这是一致的IC/CMB模型的预测，他们的X射线发射。我们已经使用档案多波长观测，以精确预测预期的最小通量在GeV波段，假设从千秒差距尺度喷流的X射线发射完全是由于IC/CMB过程。在OJ 287和PKS 1510−089这两个源中，探测到的最小伽马射线通量水平与预测一致。这两个源表现出极端的超光速自行相对于他们的喷流功率，这认为良好的对齐的IC/CMB模型所需的喷流。在PKS 1510−089的情况下，不能排除最小的伽马射线通量水平是由于可变核心的低状态，只是偶然地与IC/CMB预测相匹配。使用费米/LAT进行持续的长期监测可以通过检测重组光变曲线中的平台特征来解决这个问题，该平台特征将清楚地表明存在不可变发射成分。
Over the past two decades, the most commonly adopted explanation for high and hard X-ray emission in resolved quasar jets has been inverse-Compton upscattering of the cosmic microwave background (IC/CMB), which requires jets that remain highly relativistic on 10–1000 kpc scales. In more recent years various lines of observational evidence, including gamma-ray upper limits, have disfavored this explanation in favor of a synchrotron origin. While the IC/CMB model generally predicts a high level of gamma-ray emission, it has never been detected. Here we report the detection of a low-state Fermi/LAT gamma-ray spectrum associated with two jetted active galactic nuclei that is consistent with the predictions of the IC/CMB model for their X-ray emission. We have used archival multiwavelength observations to make precise predictions for the expected minimum flux in the GeV band, assuming that the X-ray emission from the kiloparsec-scale jet is entirely due to the IC/CMB process. In both sources—OJ 287 and PKS 1510−089—the minimum-detected gamma-ray flux level agrees with predictions. Both sources exhibit extreme superluminal proper motions relative to their jet power, which argues for the well-aligned jets required by the IC/CMB model. In the case of PKS 1510−089, it cannot be ruled out that the minimum gamma-ray flux level is due to a low state of the variable core that only matches the IC/CMB prediction by chance. Continued long-term monitoring with the Fermi/LAT could settle this issue by detecting a plateau signature in the recombined light curve that would clearly signal the presence of a nonvariable emission component.