We report sub-parsec-scale observations of the 321 GHz H2O emission line in the radio galaxy NGC 1052. The H2O line emitter size is constrained in <0.6 mas distributed on the continuum core component. The brightness temperature exceeding 106 K and the intensity variation indicate certain evidence for maser emission. The maser spectrum consists of redshifted and blueshifted velocity components spanning ∼400 km s−1, separated by a local minimum around the systemic velocity of the galaxy. The spatial distribution of maser components shows a velocity gradient along the jet direction, implying that the population-inverted gas is driven by the jets interacting with the molecular torus. We identified a significant change of the maser spectra between two sessions separated by 14 days. The maser profile showed a radial velocity drift of 127 ± 13 km s−1 yr−1 implying inward gravitational acceleration at 5000 Schwarzschild radii. The results demonstrate the feasibility of future very long baseline interferometry observations to resolve the jet–torus interacting region.

中文翻译：

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射电星系 NGC 1052 中可能存在重力加速的亚秒差距级喷射驱动水脉泽

我们报告了射电星系 NGC 1052 中 321 GHz H2O 发射线的亚秒差距观测。H2O 线发射器尺寸被限制在分布在连续介质核心组件上的 <0.6 mas。超过106 K的亮温和强度变化表明了脉泽发射的某些证据。微波激射谱由红移和蓝移速度分量组成，跨度约为 400 km s−1，由星系系统速度周围的局部最小值分隔开。微波激射器分量的空间分布显示出沿射流方向的速度梯度，这意味着粒子数反转气体是由与分子环面相互作用的射流驱动的。我们发现相隔 14 天的两个会话之间的脉泽光谱发生了显着变化。微波激射剖面显示径向速度漂移为 127 ± 13 km s−1 yr−1，这意味着 5000 个史瓦西半径处存在向内重力加速度。结果证明了未来通过超长基线干涉测量观测来解决射流-环面相互作用区域的可行性。