变化之风--NGC 1377中的分子外流？一个极端FIR过剩星系的解剖
Winds of change - a molecular outflow in NGC 1377? The anatomy of an extreme FIR-excess galaxy
摘要：
我们使用高（0。“65x0。“52，（65 x52 pc））分辨率亚毫米阵列（SMA）观测图像的CO和13 CO 2-1线发射的极端FIR过剩星系NGC 1377。我们发现明亮的，复杂的CO2 -1线发射的内部400 pc的星系。CO 2-1线有翅膀，是跟踪一个运动学的组成部分，出现垂直于线的核心。结合有趣的X形积分强度和色散图，这表明NGC 1377的分子发射由盘流出系统组成。分子量和流出速率的下限为Mout（H2）> 1 e7 Msun和dM/dt>8 Msun/yr。拟定的外流年龄估计为140万年，范围为200 pc，外流速度为140 km/s。在SMA图中，总分子量估计为Mtot（H2）= 1.5e8Msun（在400 pc的尺度上），而在内部r=29 pc，分子量估计为Mcore（H2）= 1.7e7Msun，相应的H2柱密度为N（H2）= 3.4e23cm-2，平均CO2 -1亮温为19 K。观测FIR过剩星系NGC 1377的分子特性使我们能够探测活动星系核活动的早期阶段和反馈的开始。外流的年龄支持了当前核活动是年轻的--几个百万年的概念。外流可能是由来自致密的尘埃包裹的原子核的辐射压力提供动力，但其他驱动机制也是可能的。埋源可能是活动星系核或一个非常年轻（100万年）的致密星暴。由于大小和质量的限制，我们倾向于活动星系核的假设，但还需要进一步的研究来解决这个问题。在任何一种情况下，风及其隐含的质量流出率将在5-25百万年的非常短的时间内熄灭核动力源。然而，这些气体可能无法逃离星系，最终可能会再次落回NGC 1377。
英文摘要：
We use high (0."65 x 0."52,(65x52pc)) resolution SubMillimeter Array (SMA) observations to image the CO and 13CO 2-1 line emission of the extreme FIR-excess galaxy NGC 1377. We find bright, complex CO 2-1 line emission in the inner 400 pc of the galaxy. The CO 2-1 line has wings that are tracing a kinematical component which appears perpendicular to that of the line core. Together with an intriguing X-shape of the integrated intensity and dispersion maps, this suggests that the molecular emission of NGC 1377 consists of a disk-outflow system. Lower limits to the molecular mass and outflow rate are M_out(H2)>1e7 Msun and dM/dt>8 Msun/yr. The age of the proposed outflow is estimated to 1.4Myrs, the extent to 200pc and the outflow speed to 140 km/s. The total molecular mass in the SMA map is estimated to M_tot(H2)=1.5e8 Msun (on a scale of 400 pc) while in the inner r=29 pc the molecular mass is M_core(H2)=1.7e7 Msun with a corresponding H2 column density of N(H2)=3.4e23 cm-2 and an average CO 2-1 brightness temperature of 19K. Observing the molecular properties of the FIR-excess galaxy NGC 1377 allows us to probe the early stages of nuclear activity and the onset of feedback in active galaxies. The age of the outflow supports the notion that the current nuclear activity is young - a few Myrs. The outflow may be powered by radiation pressure from a compact, dust enshrouded nucleus, but other driving mechanisms are possible. The buried source may be an AGN or an extremely young (1Myr) compact starburst. Limitations on size and mass lead us to favour the AGN scenario, but further studies are required to settle the issue. In either case, the wind with its implied mass outflow rate will quench the nuclear power source within a very short time of 5-25 Myrs. It is however possible that the gas is unable to escape the galaxy and may eventually fall back onto NGC 1377 again.
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