Arp 220分子谱线的高分辨率观测：运动学、形态学和氨温度计适用性的限制
High Resolution Observations of Molecular Lines in Arp 220: Kinematics, Morphology, and Limits on the Applicability of the Ammonia Thermometer
摘要：
我们观察到Arp 220，最近的超亮红外星系（ULIRG），超过4 GHz的K和Ka波段。我们提供了运动学，形态学的限制，并确定分子种类的尺度上解决两个核（0.6”或230 pc）。我们检测到多种分子种类，包括两个核心中的羟基。我们试探性地检测H2O在21.84 GHz的两个核，表明可能存在的微波激射发射。观察到的频率范围也包含从（J，K）=（1，1）到（5，5）的亚稳态氨跃迁，以及（9，9）反转线，它们一起是稠密分子气体的众所周知的温度计。此外，还检测到非亚稳态（4，2）和（10，9）以及可能的（3，1）线。我们对Arp 220进行标准温度分析。然而，分析是复杂的，因为标准LTE假设不成立。有迹象表明，相当大一部分的氨可能是在非亚稳态的转变，而不是只有亚稳态的。因此，非亚稳态转变对于限制温度是必不可少的。我们将所有这些数据与ALMA对该源的观测进行比较，证实了先前在两个核中观察到的其他示踪剂的流出。
英文摘要：
We observe Arp 220, the nearest Ultra-Luminous Infrared Galaxy (ULIRG), over 4 GHz in the K and Ka bands. We provide constraints for the kinematics,morphology, and identify molecular species on scales resolving both nuclei (0.6" or 230 pc). We detect multiple molecular species, including hydroxyl in both cores. We tentatively detect H2O at 21.84 GHz in both nuclei, indicating the likely presence of maser emission. The observed frequency range also contains metastable ammonia transitions from (J,K) = (1,1) to (5,5), as well as the (9,9) inversion line, which, together are a well-known thermometer of dense molecular gas. Furthermore, the non-metastable (4,2) and (10,9) and possibly the (3,1) lines are also detected. We apply a standard temperature analysis to Arp 220. However, the analysis is complicated in that standard LTE assumptions do not hold. There are indications that a substantial fraction of ammonia could be in the non-metastable transitions as opposed to only the metastable ones. Thus, the non-metastable transitions could be essential to constraining the temperature. We compare all of these data to ALMA observations of this source, confirming the outflow previously observed by other tracers in both nuclei.
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