论文标题
NGC 6822作为矮人银河进化的探针
NGC 6822 as a probe of dwarf galactic evolution
论文作者
论文摘要
NGC 6822是最接近孤立的矮人不规则的星系，距银河系。它的接近度和出色的质量（$ 10^8 m_ \ odot $，对于矮星银河）允许对其运动学特性进行详细研究。星系中心的红色巨型分支（RGB）恒星特别有趣，因为它们在垂直于银河系更扩展的HI磁盘的轴上对齐。我们使用Keck Deimos的光谱在RGB种群中检测到速度梯度。这种旋转与HI磁盘对齐，但旋转感是关于中央RGB种群的主要轴。我们测量了五个金属箱中RGB人口的旋转速度（$ V $）和速度分散（$σ$）。我们发现随着金属性的增加，旋转支撑（$ v/σ$）的增加，主要是由于分散体的减少而驱动。我们还通过将观察到的恒星运动学与NGC 6822的HI速度曲线联系起来，以$ -0.5 $ 〜kpc/dex推导出低金属恒星的径向距离。虽然倒金属性梯度样可以解释为外部地层场景的证据，但它可能表明恒星反馈会随着时间的推移而扰乱了一个中央恒星形成的星系。
NGC 6822 is the closest isolated dwarf irregular galaxy to the Milky Way. Its proximity and stellar mass ($10^8 M_\odot$, large for a dwarf galaxy) allow for a detailed study of its kinematic properties. The red giant branch (RGB) stars at the galaxy's center are particularly interesting because they are aligned on an axis perpendicular to the galaxy's more extended HI disk. We detected a velocity gradient among the RGB population using spectra from Keck DEIMOS. This rotation is aligned with the HI disk, but the sense of rotation is about the major axis of the central RGB population. We measured the rotation velocity ($v$) and velocity dispersion ($σ$) of the RGB population in five metallicity bins. We found an increase of rotation support ($v/σ$) with increasing metallicity, driven primarily by decreasing dispersion. We also deduced an increasing radial distance for lower metallicity stars at $-0.5$~kpc/dex by relating the observed stellar kinematics to position via NGC 6822's HI velocity curve. While the inverted metallicity gradient-like could be interpreted as evidence for an outside-in formation scenario, it may instead indicate that stellar feedback disturbed a centrally star forming galaxy over time.
