由 OH 巨型脉泽追踪的亮红外星系 Zw049.057 的喷泉
The fountain of the luminous infrared galaxy Zw049.057 as traced by its OH megamaser
AI总结：
本研究利用 e-MERLIN 与 ALMA 观测 Zw049.057 核区的 OH、H2CO 巨型脉泽及 HCN 发射，识别出慢速宽角喷泉流与可逃逸的快速准直外流。
摘要：
高分辨率（0."037–0."13 [10–35 pc]）e-MERLIN（λ6–18 cm）和（0."024 [6.5 pc]）ALMA（λ1.1 mm）观测被用于对亮红外星系 Zw049.057 的核区（<100 pc）内的 OH（羟基）和 H2CO（甲醛）巨型脉泽发射以及 HCN 3→2 发射成像。Zw049.057 拥有一个致密遮蔽核（CON），因此代表了一类常与内流和外流运动相关的星系。在核区 <30 pc（<0."1）范围内探测到甲醛巨型脉泽发射，其追踪沿盘主轴分布的结构。OH 巨型脉泽（OHM）发射沿盘的短轴被探测到，距核约 30 pc（0."1），在该处表现出速度梯度，极值分别位于盘东南（SE）侧的 -20 km/s 和盘西北（NW）侧的 -110 km/s。HCN 3→2 发射揭示了沿盘短轴延伸至约 60 pc（0."2）的延展发射。对短轴 HCN 发射的分析揭示了高速特征，延伸至 600 km/s，在 SE 侧红移，在 NW 侧蓝移。我们提出，高速 HCN 发射追踪一个速度 >250 km/s 的快速准直外流，该外流被由 OHM 发射追踪的宽角、速度约 50 km/s 的慢速外流所包裹。对外流运动学的分析表明，慢速宽角外流不会达到逃逸速度，而是会落回星系盘，演化为所谓的喷泉流，而由 HCN 发射追踪的快速准直外流则可能逃离核区。我们认为核区缺少 OHM 发射是由于那里的高密度。尽管与外流相关的 OHM 是常规 OHM 发射的例外，但我们预期它们在同时拥有 OHM 和 H2CO 巨型脉泽的 CON 源中很常见。
英文摘要：
High resolution (0."037-0."13 [10-35 pc]) e-MERLIN ($\lambda6-18$ cm) and (0."024 [6.5 pc]) ALMA ($λ1.1$ mm) observations have been used to image OH (hydroxyl) and H$_2$CO (formaldehyde) megamaser emission, and HCN 3->2 emission towards the nuclear (<100 pc) region of the luminous infrared galaxy Zw049.057. Zw049.057 hosts a compact obscured nucleus (CON), thus representing a class of galaxies that are often associated with inflow and outflow motions. Formaldehyde megamaser emission is detected towards the nuclear region, <30 pc (<0."1), and traces a structure along the disk major axis. OH megamaser (OHM) emission is detected along the minor axis of the disk, ~30 pc (0."1) from the nucleus, where it exhibits a velocity gradient with extrema of -20 km/s south-east (SE) of the disk and -110 km/s north-west (NW) of the disk. HCN 3->2 emission reveals extended emission, along the disk minor axis out to ~60 pc (0."2). Analysis of the minor axis HCN emission reveals high-velocity features, extending out to 600 km/s, redshifted on the SE side and blueshifted on the NW side. We propose that the high-velocity HCN emission traces a fast >250 km/s and collimated outflow, that is enveloped by a wide-angle and slow ~50 km/s outflow that is traced by the OHM emission. Analysis of the outflow kinematics suggests that the slow wide-angle outflow will not reach escape velocity and instead will fall back to the galaxy disk, evolving as a so-called fountain flow, while the fast collimated outflow traced by HCN emission will likely escape the nuclear region. We suggest that the absence of OHM emission in the nuclear region is due to high densities there. Even though OHMs associated with outflows are an exception to conventional OHM emission, we expect them to be common in CON sources that host both OHM and H$_2$CO megamasers.
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