另一个难题是：Mrk231中的快速PDKEEPAAA流出
Another piece of the puzzle: the fast HI outflow in Mrk231
摘要：
我们提出的检测，韦斯特博克综合射电望远镜（WSRT）和卡尔Jansky甚大阵（VLA），在超亮红外星系Mrk 231的快速HI 21厘米流出。流出被观察到作为浅HI吸收蓝移~1300 km/s相对于系统速度和位于对内部kpc的射电源。流出气体的柱密度估计在5 ~ 15x10^18 Tspin cm^-2之间。我们推导出T自旋在400-2000 K之间，密度为n_HI~10-100 cm^-3。我们的研究结果证实了Mrk 231外流的多相性。虽然不能排除射电等离子体和周围介质之间相互作用的影响，但能量学和缺乏明确的kpc尺度喷流表明，HI外流最有可能的起源是广角核风，正如早先提出的解释中性外流跟踪碘化钠和分子气体。我们的研究结果表明，HI组件是存在于快速流出，无论加速机制（风与喷气驱动），它必须与共同的属性的预相互作用气体。考虑到所观察到的柱密度的相似性，HI外流可能代表了在NaI中较大尺度上确定的宽风的内部。HI流出的质量流出率似乎不像在分子气体中观察到的那样大。这些特征表明，HI可能代表气体快速冷却过程中的一个短暂的中间阶段。我们还获得了比以前更深的连续图像。在~1arcsec的分辨率下，我们没有看到kpc尺度的喷流。相反，我们探测到一个发射平台，可能是由于恒星形成，围绕明亮的核区域。我们还检测到一个准直不良的桥梁，这可能代表通道喂养南瓣。
英文摘要：
We present the detection, performed with the Westerbork Synthesis Radio Telescope (WSRT) and the Karl Jansky Very Large Array (VLA), of a fast HI 21-cm outflow in the ultra-luminous infrared galaxy Mrk 231. The outflow is observed as shallow HI absorption blueshifted ~1300 km/s with respect to the systemic velocity and located against the inner kpc of the radio source. The outflowing gas has an estimated column density between 5 and 15x10^18 Tspin cm^-2. We derive the Tspin to lie in the range 400-2000 K and the densities are n_HI~10-100 cm^-3. Our results confirm the multiphase nature of the outflow in Mrk231. Although effects of the interaction between the radio plasma and the surrounding medium cannot be ruled out, the energetics and the lack of a clear kpc-scale jet suggest that the most likely origin of the HI outflow is a wide-angle nuclear wind, as earlier proposed to explain the neutral outflow traced by NaI and molecular gas. Our results suggest that an HI component is present in fast outflows regardless of the acceleration mechanism (wind vs jet driven) and that it must be connected with common properties of the pre-interaction gas. Considering the observed similarity of their column densities, the HI outflow likely represents the inner part of the broad wind identified on larger scales in NaI. The mass outflow rate of the HI outflow does not appear to be as large as the one observed in molecular gas. These characteristics suggest that the HI may represent a short intermediate phase in the rapid cooling of the gas. We also obtained deeper continuum images than previously available. At the resolution of ~1arcsec we do not see a kpc-scale jet. Instead, we detect a plateau of emission, likely due to star formation, surrounding the bright nuclear region. We also detect a poorly collimated bridge which may represent the channel feeding the southern lobe.
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