问题的核心：无凸起矮星系和暗物质核心的起源
At the heart of the matter: the origin of bulgeless dwarf galaxies and Dark Matter cores
摘要：
近20年来，“矮”星系的性质一直在挑战星系形成的冷暗物质（CDM）范式。大多数观测到的矮星系由一个旋转的恒星盘组成，嵌入一个大质量的DM晕中，具有近恒定密度的核心。然而，基于CDM方案的模型总是形成具有致密球状恒星“凸起”和陡峭中心DM轮廓的星系，因为低角动量重子和DM通过吸积和反复合并下沉到星系中心。降低CDM晕中心密度的过程已经被确认，但还没有将理论与现今矮星的观测相协调。这种失败对于CDM模型来说可能是灾难性的，可能需要不同的DM粒子候选者。这封信提出了新的流体动力学模拟的Lambda$CDM框架中的类似物的矮星系，无凸起和浅中央DM配置文件，形成。这是通过分解不均匀的星际介质来实现的，这导致了超新星爆炸产生的强烈外流，从而消除了低角动量气体。这抑制了隆起的形成，并将中央千秒差距内的暗物质密度降低到不到一半。因此，现实的矮星系被证明是一个自然的结果星系形成的CDM方案。
英文摘要：
For almost two decades the properties of "dwarf" galaxies have challenged the Cold Dark Matter (CDM) paradigm of galaxy formation. Most observed dwarf galaxies consists of a rotating stellar disc embedded in a massive DM halo with a near constant-density core. Yet, models based on the CDM scenario invariably form galaxies with dense spheroidal stellar "bulges" and steep central DM profiles, as low angular momentum baryons and DM sink to the center of galaxies through accretion and repeated mergers. Processes that decrease the central density of CDM halos have been identified, but have not yet reconciled theory with observations of present day dwarfs. This failure is potentially catastrophic for the CDM model, possibly requiring a different DM particle candidate. This Letter presents new hydrodynamical simulations in a Lambda$CDM framework where analogues of dwarf galaxies, bulgeless and with a shallow central DM profile, are formed. This is achieved by resolving the inhomogeneous interstellar medium, resulting in strong outflows from supernovae explosions which remove low angular momentum gas. This inhibits the formation of bulges and decreases the dark-matter density to less than half within the central kiloparsec. Realistic dwarf galaxies are thus shown to be a natural outcome of galaxy formation in the CDM scenario.
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