MAGNETIZATION DEGREE AT THE JET BASE OF M87 DERIVED FROM THE EVENT HORIZON TELESCOPE DATA: TESTING THE MAGNETICALLY DRIVEN JET PARADIGM
MAGNETIZATION DEGREE AT THE JET BASE OF M87 DERIVED FROM THE EVENT HORIZON TELESCOPE DATA: TESTING THE MAGNETICALLY DRIVEN JET PARADIGM
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DOI：
10.1088/0004-637x/803/1/30
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发表时间：
2015-02
期刊：
影响因子：
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通讯作者：
M. Kino;Fumio Takahara;K. Hada;K. Akiyama;H. Nagai;B. Sohn
中科院分区：
文献类型：
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作者：
M. Kino;Fumio Takahara;K. Hada;K. Akiyama;H. Nagai;B. Sohn
我们利用 Doeleman 等人获得的事件视界望远镜 (EHT) 在 230 GHz 的观测数据来探索 M87 喷气机底座的磁化程度。利用Kino等人的方法，我们推导了EHT探测到的致密区域（EHT区域）中半高宽为40的磁场（UB）和电子和正电子（U±？>）的能量密度为？>。首先，我们假设 EHT 区域中存在同步加速器自吸收 (SSA) 的光学厚区域。然后，我们发现SSA厚区域不应该太大，以免在EHT区域产生过度的坡印廷功率。 SSA厚区域的角度大小和磁场强度的允许范围分别为21as≤θthick≤26.3asβ>和50G≤Btot≤124Gβ>。相应地，此时U B ≫ U ± β > 成立。我们利用 Kuo 等人在 230 GHz 下获得的法拉第旋转测量结果进一步研究了等离子体的成分和质子的能量密度。然后，我们发现 U B ≫ U ± + U p ?> 在 SSA 厚区域仍然成立。其次，我们研究 EHT 区域完全 SSA 薄时的情况。然后，我们发现 U B ≫ U ± ?> 仍然成立，除非质子是相对论的。因此，我们得出的结论是，M87 中的磁驱动喷射场景在接近最内层稳定圆形轨道尺度的能量学方面是可行的，除非 EHT 区域完全是 SSA 薄层且相对论性质子占主导地位。
We explore the degree of magnetization at the jet base of M87 by using the observational data of the event horizon telescope (EHT) at 230 GHz obtained by Doeleman et al. By utilizing the method in Kino et al., we derive the energy densities of the magnetic fields (UB) and electrons and positrons ( U ± ?> ) in the compact region detected by EHT (the EHT region) with its FWHM size 40 as ?> . First, we assume that an optically thick region for synchrotron self-absorption (SSA) exists in the EHT region. Then, we find that the SSA-thick region should not be too large, in order to not overproduce the Poynting power at the EHT region. The allowed ranges of the angular size and the magnetic-field strength of the SSA-thick region are 21 as ≤ θ thick ≤ 26.3 as ?> and 50 G ≤ B tot ≤ 124 G ?> , respectively. Correspondingly, U B ≫ U ± ?> is realized in this case. We further examine the composition of plasma and energy density of protons by utilizing the Faraday rotation measurement at 230 GHz obtained by Kuo et al. Then, we find that U B ≫ U ± + U p ?> still holds in the SSA-thick region. Second, we examine the case when the EHT region is fully SSA-thin. Then, we find that U B ≫ U ± ?> still holds unless protons are relativistic. Thus, we conclude that the magnetically driven jet scenario in M87 is viable in terms of energetics close to the Innermost Stable Circular Orbit scale unless the EHT region is fully SSA-thin and relativistic protons dominated.