ALMA Observations of HCN and HCO+ Outflows in the Merging Galaxy NGC 3256
ALMA Observations of HCN and HCO+ Outflows in the Merging Galaxy NGC 3256
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DOI：
10.3847/1538-4357/aae82a
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发表时间：
2018-10
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影响因子：
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通讯作者：
T. Michiyama;D. Iono;K. Śliwa;A. Bolatto;K. Nakanishi;J. Ueda;T. Saito;M. Ando;T. Yamashita;M. Yun
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作者：
T. Michiyama;D. Iono;K. Śliwa;A. Bolatto;K. Nakanishi;J. Ueda;T. Saito;M. Ando;T. Yamashita;M. Yun
我们报告了~ 2″分辨率阿塔卡马大毫米/亚毫米阵列观测到的HCN（1-0）、HCO+(1-0)、CO（1-0）、CO（2 - 1）和CO（3-2）线，这些线指向附近合并的双核星系NGC 3256。我们发现，在HCN（1-0）和HCO+(1-0)发射中追踪到的高密度气体流出与从南核发出的弥漫分子流出同时存在，其中低光度的活动星系核（AGN）被认为是远红外光度的主要来源。另一方面，在与北核相关的流出区未检测到相同的谱线，北核的主要热源可能与星暴活动有关，没有明显的AGN迹象。南侧出口的HCO+ (1-0)/CO（1-0）线比（即致密气体馏分）和CO (3-2)/CO（1-0）线比（分别为0.20±0.04和1.3±0.2）均大于南侧核（分别为0.08±0.01和0.7±0.1）。通过研究南部出口中每个速度分量的线比，我们发现致密气体分数增加，CO (3-2)/CO（1-0）线比向最大速度偏移减小。这表明存在两相（弥漫性和块状）流出。产生这种两相流出的一种可能的情况是射流和星际介质之间的相互作用，这可能引发与流出相关的冲击和/或恒星形成。
We report ∼2″ resolution Atacama Large Millimeter/submillimeter Array observations of the HCN (1–0), HCO+ (1–0), CO (1–0), CO (2–1), and CO (3–2) lines toward the nearby merging double-nucleus galaxy NGC 3256. We find that the high-density gas outflow traced in HCN (1–0) and HCO+ (1–0) emission is colocated with the diffuse molecular outflow emanating from the southern nucleus, where a low-luminosity active galactic nucleus (AGN) is believed to be the dominant source of the far-infrared luminosity. On the other hand, the same lines were undetected in the outflow region associated with the northern nucleus, whose primary heating source is likely related to starburst activity without obvious signs of an AGN. Both the HCO+ (1–0)/CO (1–0) line ratio (i.e., dense gas fraction) and the CO (3–2)/CO (1–0) line ratio are larger in the southern outflow (0.20 ± 0.04 and 1.3 ± 0.2, respectively) than in the southern nucleus (0.08 ± 0.01 and 0.7 ± 0.1, respectively). By investigating these line ratios for each velocity component in the southern outflow, we find that the dense gas fraction increases and the CO (3–2)/CO (1–0) line ratio decreases toward the largest velocity offset. This suggests the existence of a two-phase (diffuse and clumpy) outflow. One possible scenario to produce such a two-phase outflow is an interaction between the jet and the interstellar medium, which possibly triggers shocks and/or star formation associated with the outflow.