Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, USA.
Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany.
Nature. 2018 Apr;556(7701):345-348. doi: 10.1038/s41586-018-0033-2. Epub 2018 Apr 18.
Theoretical models and numerical simulations have established a framework of galaxy evolution in which galaxies merge and create dual supermassive black holes (with separations of one to ten kiloparsecs), which eventually sink into the centre of the merger remnant, emit gravitational waves and coalesce. The merger also triggers star formation and supermassive black hole growth, and gas outflows regulate the stellar content. Although this theoretical picture is supported by recent observations of starburst-driven and supermassive black hole-driven outflows, it remains unclear how these outflows interact with the interstellar medium. Furthermore, the relative contributions of star formation and black hole activity to galactic feedback remain unknown. Here we report observations of dual outflows in the central region of the prototypical merger NGC 6240. We find a black-hole-driven outflow of [O III] to the northeast and a starburst-driven outflow of Hα to the northwest. The orientations and positions of the outflows allow us to isolate them spatially and study their properties independently. We estimate mass outflow rates of 10 and 75 solar masses per year for the Hα bubble and the [O III] cone, respectively. Their combined mass outflow is comparable to the star formation rate , suggesting that negative feedback on star formation is occurring.
理论模型和数值模拟为星系演化建立了一个框架，在这个框架中，星系合并并产生了两个超大质量黑洞（分离度为一到十千秒差距），最终落入合并残余物的中心，发射引力波并合并。合并还会引发恒星形成和超大质量黑洞的生长，并通过气体外流来调节恒星含量。尽管这一理论图景得到了最近对星暴驱动和超大质量黑洞驱动外流的观测的支持，但这些外流如何与星际介质相互作用仍不清楚。此外，恒星形成和黑洞活动对星系反馈的相对贡献仍不清楚。在这里，我们报告了对原型合并 NGC 6240 中心区域的双重外流的观测结果。我们发现了一个向东北方向的黑洞驱动的[O III]外流和一个向西北方向的星暴驱动的 Hα 外流。外流的方向和位置使我们能够在空间上隔离它们，并独立研究它们的性质。我们分别估计 Hα 泡和[O III]锥的质量外流率为每年 10 和 75 个太阳质量。它们的总质量外流与恒星形成率相当，表明对恒星形成的负反馈正在发生。
