半人马座A喷流发射和准直的事件视界望远镜观测
Event Horizon Telescope observations of the jet launching and collimation in Centaurus A
摘要：
甚长基线干涉测量（VLBI）的活动星系核在毫米波长的观测有能力揭示河外射电喷流的发射和初始准直区域，下至附近源的$10-100$引力半径（$r_g=GM/c^2$）尺度。半人马座A是距离地球最近的无线电噪声源。它弥补了Messier 87中的超大质量黑洞（SMBHs）和我们银河系中心之间的质量和吸积率差距。然而，到目前为止，$-43^{\circ}$的大南部沉降阻止了半人马座A在$λ1$ cm以下的VLBI成像。在这里，我们显示的毫米VLBI图像的源，这是我们获得的事件视界望远镜在$228$ GHz。与以前的观测结果相比，我们以高10倍的频率和高16倍的分辨率拍摄了半人马座A的喷流，从而探测了亚光日结构。我们揭示了一个高度准直，不对称的边缘增亮射流以及较暗的反喷流。我们发现半人马座A的源结构非常类似于${\sim}500r_g$尺度上Messier 87中的喷流。此外，我们确定的位置半人马座A的SMBH相对于其解决喷气核心$λ1.3$毫米，并得出结论，源的事件视界的阴影应该是可见的太赫兹频率。这个位置进一步支持了黑洞在广泛质量范围内的普遍尺度不变性。
英文摘要：
Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimeter wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to $10-100$ gravitational radii ($r_g=GM/c^2$) scales in nearby sources. Centaurus A is the closest radio-loud source to Earth. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our galactic center. A large southern declination of $-43^{\circ}$ has however prevented VLBI imaging of Centaurus A below $λ1$cm thus far. Here, we show the millimeter VLBI image of the source, which we obtained with the Event Horizon Telescope at $228$GHz. Compared to previous observations, we image Centaurus A's jet at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly-collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that Centaurus A's source structure resembles the jet in Messier 87 on ${\sim}500r_g$ scales remarkably well. Furthermore, we identify the location of Centaurus A's SMBH with respect to its resolved jet core at $λ1.3$mm and conclude that the source's event horizon shadow should be visible at THz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses.
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