Department of Physics, University of Wisconsin-Madison, Madison, WI, USA.
Department of Astronomy, University of Wisconsin-Madison, Madison, WI, USA.
Nature. 2020 Sep;585(7824):203-206. doi: 10.1038/s41586-020-2663-4. Epub 2020 Sep 9.
The dominant gaseous structure in the Galactic halo is the Magellanic Stream. This extended network of neutral and ionized filaments surrounds the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC), the two most massive satellite galaxies of the Milky Way. Recent observations indicate that the LMC and SMC are on their first passage around the Galaxy, that the Magellanic Stream is made up of gas stripped from both clouds and that the majority of this gas is ionized. Although it has long been suspected that tidal forces and ram-pressure stripping contributed to the formation of the Magellanic Stream, models have not been able to provide a full understanding of its origins. Several recent developments-including the discovery of dwarf galaxies associated with the Magellanic group, determination of the high mass of the LMC, detection of highly ionized gas near stars in the LMC and predictions of cosmological simulations-support the existence of a halo of warm (roughly 500,000 kelvin) ionized gas around the LMC (the 'Magellanic Corona'). Here we report that, by including this Magellanic Corona in hydrodynamic simulations of the Magellanic Clouds falling onto the Milky Way, we can reproduce the Magellanic Stream and its leading arm. Our simulations explain the filamentary structure, spatial extent, radial-velocity gradient and total ionized-gas mass of the Magellanic Stream. We predict that the Magellanic Corona will be unambiguously observable via high-ionization absorption lines in the ultraviolet spectra of background quasars lying near the LMC.
在银河晕中占主导地位的气态结构是麦哲伦流。这个由中性和电离丝状纤维组成的扩展网络环绕着大麦哲伦云（LMC）和小麦哲伦云（SMC），这是银河系两个最大的卫星星系。最近的观测表明，LMC 和 SMC 正处于它们第一次绕银河系运行的过程中，麦哲伦流是由两个云团中剥离的气体组成的，而且大部分气体是电离的。尽管人们早就怀疑潮汐力和冲压剥离对麦哲伦流的形成有贡献，但模型还不能完全理解它的起源。最近的几项发展——包括发现与麦哲伦星系相关的矮星系、确定 LMC 的高质量、在 LMC 中的恒星附近探测到高度电离的气体以及宇宙学模拟的预测——都支持在 LMC（“麦哲伦冕”）周围存在一个温暖（约 50 万开尔文）电离气体晕。在这里，我们报告说，通过在对麦哲伦云落入银河系的流体动力学模拟中包含这个麦哲伦冕，我们可以重现麦哲伦流及其前缘。我们的模拟解释了麦哲伦流的丝状结构、空间延伸、径向速度梯度和总电离气体质量。我们预测，通过 LMC 附近背景类星体的紫外光谱中的高电离吸收线，将可以明确观测到麦哲伦冕。
