SMHASH：一个新的中红外RR对Local Group矮球状星系Sculptor的天琴座距离测定
SMHASH: A new mid-infrared RR Lyrae distance determination for the Local Group dwarf spheroidal galaxy Sculptor
摘要：
我们提出了一个新的距离估计银河系矮球状卫星雕塑家获得的多历元中红外观测的RR天琴座星。作为SMHASH计划的一部分，斯皮策太空望远镜上的红外阵列相机已经获得了3.6 μm的观测结果。测得42个RRL的中红外线曲线，并由此测得Sculptor距离模量μ = 19.60 $\pm$ 0.02（统计学）$\pm$ 0.04（光度）磁（其中$σ_{sys}=$ = 0.09等），使用从银河系球状星团M4导出的3.6 μm经验周期光度关系，或μ = 19.57 $\pm$ 0.02（统计）$\pm$ 0.04（光度）等（其中$σ_{sys}=$ = 0.11等），使用最近从大麦云球状星团网壳中导出的相同通带的经验关系。这两个测量值在很好的协议，在以前的作品与雕塑家RR天琴座恒星在光学波段，也与最近的近红外RR天琴座的结果是一致的。最好的协议与文献中发现后者的模量，这是相当于一个距离d = 82 $\pm$ 1（统计）$\pm$ 2（光度）kpc（与$σ_{sys}=$ = 4 kpc）。最后，使用一个子样本的RR天琴座恒星光谱金属丰度，我们证明，这些距离估计不受金属丰度效应。
英文摘要：
We present a new distance estimation for the Milky Way dwarf spheroidal satellite Sculptor obtained from multi-epoch mid-infrared observations of RR Lyrae stars. The 3.6 μm observations have been acquired with the Infrared Array Camera on board the Spitzer Space Telescope as part of the SMHASH Program. Mid-infrared light curves for 42 RRL were obtained, from which we measured Sculptor's distance modulus to be μ = 19.60 $\pm$ 0.02 (statistical) $\pm$ 0.04 (photometric) mag (with $σ_{sys}=$ = 0.09 mag), using the 3.6 μm empirical period-luminosity relations derived from the Galactic globular cluster M4, or μ = 19.57 $\pm$ 0.02 (statistical) $\pm$ 0.04 (photometric) mag (with $σ_{sys}=$ = 0.11 mag) using empirical relations in the same passband recently derived from the Large Magellanic Cloud globular cluster Reticulum. Both these measurements are in good agreement with values presented in previous works with Sculptor RR Lyrae stars in optical bands, and are also consistent with recent near-infrared RR Lyrae results. Best agreement with the literature is found for the latter modulus which is equivalent to a distance of d = 82 $\pm$ 1 (statistical) $\pm$ 2 (photometric) kpc (with $σ_{sys}=$ = 4 kpc). Finally, using a subsample of RR Lyrae stars with spectroscopic metallicities, we demonstrate that these distance estimates are not affected by metallicity effects.
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