在NGC 1275中发现一个新的亚秒差距反喷流：倾角和环境
Discovery of a new subparsec counterjet in NGC 1275: the inclination angle and the environment
摘要：
我们报告检测到一个新的功能，在英仙座集群的NGC 1275中心，托管的无线电源3C 84。在最近的15和43 GHz VLBA图像中，这一特征出现在中央核心以北约2 mas（约0.8 pc）处，似乎是一个已知的射电喷流向核心南部扩张的反喷流。显然，这两架飞机是在2005年左右的一次爆发中诞生的。根据两股喷流距离地核的视长度之比，我们发现喷流与视线的夹角为θ=65^ \circ \pm 16^ \circ，这与1959年左右的一次活动产生的外部喷流的夹角相差不大，限制了关于喷流伽马射线发射的理论。新的北方急流有一个强烈的反向频谱与南方急流。这表明中心黑洞被一个密度大于10^5 cm^-3的亚秒差距尺度的吸积盘所包围。反喷流的亮度表明，圆盘是高度不均匀的。如果当前的喷流活动与过去的平均值相似，则喷流方向的环境气体密度约为8 cm^-3。
英文摘要：
We report the detection of a new feature at the centre of NGC 1275 in the Perseus cluster, hosting the radio source 3C 84. This feature emerges ~ 2 mas (~ 0.8 pc) north of the central core in recent 15 and 43 GHz VLBA images, and seems to be the counterjet to a known radio jet expanding to the south of the core. Apparently, the two jets were born through an outburst around 2005. From the ratio of the apparent lengths of the two jets from the core, we found that the jet angle to the line of sight is θ=65^\circ\pm 16^\circ, which is not much different from the angle of the outer jets generated by an activity around 1959 and constrains theories on gamma-ray emission from jets. The new northern jet has a strongly inverted spectrum in contrast with the southern jet. This suggests that the central black hole is surrounded by a subparsec-scale accretion disk with the density of >~ 10^5 cm^-3. The brightness of the counterjet suggests that the disk is highly inhomogeneous. The ambient gas density in the direction of the jet is ~ 8 cm^-3 if the current jet activity is similar to the past average.
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