We present kinematical profiles and metallicity for the M31 dwarf spheroidal (dSph) satellite galaxy Andromeda?II (And?II) based on Keck DEIMOS spectroscopy of 531 red giant branch stars. Our kinematical sample is among the largest for any M31 satellite and extends out to two effective radii (r eff = 53 = 1.1?kpc). We find a mean systemic velocity of –192.4 ± 0.5?km?s–1 and an average velocity dispersion of σ v = 7.8 ± 1.1?km?s–1. While the rotation velocity along the major axis of And?II is nearly zero (1?km?s–1), the rotation along the minor axis is significant with a maximum rotational velocity of v max = 8.6 ± 1.8?km?s–1. We find a kinematical major axis, with a maximum rotational velocity of v max = 10.9 ± 2.4?km?s–1, misaligned by 67° to the isophotal major axis. And?II is thus the first dwarf galaxy with evidence for nearly prolate rotation with a v max/σ v = 1.1, although given its ellipticity of = 0.10, this object may be triaxial. We measured metallicities for a subsample of our data, finding a mean metallicity of [Fe/H] = –1.39 ± 0.03?dex and an internal metallicity dispersion of 0.72 ± 0.03 ?dex. We find a radial metallicity gradient with metal-rich stars more centrally concentrated, but do not observe a significant difference in the dynamics of the two metallicity populations. And?II is the only known dwarf galaxy to show minor axis rotation, making it a unique system whose existence offers important clues on the processes responsible for the formation of dSphs.
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机译：我们基于531个红色巨型分支星的Keck DEIMOS光谱，介绍了M31矮球体（dSph）卫星星系仙女座II（And？II）的运动学特征和金属性。我们的运动学样本是所有M31卫星中最大的，并且延伸到两个有效半径（r eff = 53 = 1.1？kpc）。我们发现系统平均速度为–192.4±0.5？km？s–1，平均速度分散为σv = 7.8±1.1？km？s–1。尽管沿着And？II主轴的旋转速度几乎为零（<1？km？s-1），但沿着短轴的旋转却很明显，最大旋转速度为v max = 8.6±1.8？km？s –1。我们找到了一条运动主轴，其最大旋转速度为v max = 10.9±2.4？km？s–1，与等距主轴偏离了67°。因此，？II是第一个矮星系，有证据证明其近扁长旋转，v max /σv = 1.1，尽管椭圆率= 0.10，该物体可能是三轴的。我们为数据的子样本测量了金属度，发现平均金属度[Fe / H] = –1.39±0.03？dex，内部金属度分散度为0.72±0.03？dex。我们发现了径向金属度梯度，其中富金属的恒星更集中地集中，但是没有观察到两个金属度总体的动力学有显着差异。 II是唯一已知的显示短轴旋转的矮星系，这使它成为一个独特的系统，它的存在为形成dSph的过程提供了重要的线索。
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