Galactoseismology：发现一个后退的变星晕星团
Galactoseismology: Discovery of a cluster of receding, variable halo stars
摘要：
从观测到的暗物质对星系盘的影响（即Galactoseismology）来描述以暗物质为主的矮星系的动力学特征仍然是一个难以实现的目标。在这里，我们提出了初步的光谱观测结果的三个集群造父候选人确定从$K$波段光变曲线走向诺玛。这些恒星的平均日心径向速度为$\sim$ 156 km/s，这是大的，不同于银河系的恒星盘。因此，这些位于$l \sim 333 ^\circ$和$b \sim -1 ^\circ$的天体是晕星;使用I型造父变星的$3.6~\micron$周期光度关系，它们的位置为$\sim$ 73 kpc。我们正在进行的$I$波段光度测定表明，与从$K_{s}$波段光变曲线确定的周期相同的时间尺度上的可变性。由$K$带周期光度关系和3.6 $\micron$周期光度关系确定的距离是相当的。观测到的这些恒星的径向速度与动力学模型的预测大致一致。如果这些恒星确实是预测中扰动银河系外HI盘的矮星系的成员，这将标志着Galactoseismology的首次应用。
英文摘要：
A dynamical characterization of dark matter dominated dwarf galaxies from their observed effects on galactic disks (i.e. Galactoseismology) has remained an elusive goal. Here, we present preliminary results from spectroscopic observations of three clustered Cepheid candidates identified from $K$-band light curves towards Norma. The average heliocentric radial velocity of these stars is $\sim$ 156 km/s, which is large and distinct from that of the Galaxy's stellar disk. These objects at $l \sim 333 ^\circ$ and $b \sim -1 ^\circ$ are therefore halo stars; using the $3.6~\micron$ period-luminosity relation of Type I Cepheids, they are at $\sim$ 73 kpc. Our ongoing $I$-band photometry indicates variability on the same time scale as the period determined from the $K_{s}$-band light curve. Distances determined from the $K$-band period-luminosity relation and the 3.6 $\micron$ period-luminosity relation are comparable. The observed radial velocity of these stars agrees roughly with predictions from dynamical models. If these stars are indeed members of the predicted dwarf galaxy that perturbed the outer HI disk of the Milky Way, this would mark the first application of Galactoseismology.
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