一匹英雄的黑马：在飞马座发现一颗超微弱的Milky Way卫星
A Hero's Dark Horse: Discovery of an Ultra-Faint Milky Way Satellite in Pegasus
摘要：
我们报告在飞马座发现了一个超微弱的银河系卫星星系。通过将我们的过密度检测算法应用于SDSS-DR 10来检测恒星的浓度，并通过4米布兰科望远镜的暗能量相机的更深测光来确认。拟合模型等时线表明，飞马座III这一天体的特征是在日心距离为$205\pm20$千秒差距处有一个古老而贫金属的恒星星族（[Fe/H] $\sim-2.1$）。这个新的恒星系统估计半光半径为$r_h=78^{+30}_{-24}$ pc，总光度为$M_{V}\sim-4.1\pm0.5$，在大小光度平面上属于矮星系。飞马座III在空间上接近MW卫星双鱼座II。这两个可能是物理关联，类似于狮子座IV和狮子座V对。飞马座III也与广阔的极地结构很好地对齐，这表明可能存在物理联系。
英文摘要：
We report the discovery of an ultra-faint Milky Way satellite galaxy in the constellation of Pegasus. The concentration of stars was detected by applying our overdensity detection algorithm to the SDSS-DR 10 and confirmed with deeper photometry from the Dark Energy Camera at the 4-m Blanco telescope. Fitting model isochrones indicates that this object, Pegasus III, features an old and metal-poor stellar population ([Fe/H]$\sim-2.1$) at a heliocentric distance of $205\pm20$ kpc. The new stellar system has an estimated half-light radius of $r_h=78^{+30}_{-24}$ pc and a total luminosity of $M_{V}\sim-4.1\pm0.5$ that places it into the domain of dwarf galaxies on the size--luminosity plane. Pegasus III is spatially close to the MW satellite Pisces II. It is possible that the two might be physically associated, similar to the Leo IV and Leo V pair. Pegasus III is also well aligned with the Vast Polar Structure, which suggests a possible physical association.
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