论文标题
通过人口II，恒星距离指标距离本地组星系的距离。 ii。 Fornax矮人球形
Distances to Local Group Galaxies via Population II, Stellar Distance Indicators. II. The Fornax Dwarf Spheroidal
论文作者
论文摘要
我们使用Las Campanas天文台的Magellan-Baaade望远镜获得了三个独立的人群II距离模量，使用宽场，基于地面的$ vi $成像，该模量使用了宽阔的，地面的$ vi $成像。在使用GAIA EDR3适当的运动中减去前景星星后，我们测量了红色巨型分支（TRGB）的$ i $ band Tim $ i_0^\ Mathrm {trgb} = 16.753 \ pm 0.03_ \ pm 0.03_ \ pm mathrm {stat}} $μ_0^\ mathrm {trgb} = 20.80 \ pm 0.037_ \ mathrm {stat} \ pm 0.057_ \ mathrm {sys} $ mag mag的模量。我们确定了与模板平均幅度的RR Lyrae（RRL）距离，并在文献中采用了时期。采用GAIA DR2校准第一个载体RRL期间luminitus和周期之间的关系，我们发现$μ_0^\ mathrm {plz} = 20.74 \ pm 0.01_ \ pm 0.01_ \ mathrm {stat} \ pm 0.12_ pm 0.12_ \ pm 0.12_ \ sys} \ pm 0.02_ \ mathrm {stat} \ pm 0.07_ \ mathrm {sys} $ mag。最后，我们确定了距离Fornax的水平分支（HB）和两个银河球状簇校准器的距离，给出了$μ_0^\ Mathrm {Hb} = 20.83 \ pm 0.03_ \ pm 0.03_ \ Mathrm {stat} \ pm pm 0.09_ \ pm 0.09_ \ mathrm {sys} $。这些距离均来自均质iMac的光度法，固定在独立的几何零点上，并利用不同类别的恒星。因此，我们平均在独立的不确定性上平均报告，并报告组合的距离模量$ \langleμ_0\ rangle = 20.770 \ pm 0.042_ \ mathrm {stat} \ pm 0.024_ \ pm 0.024_ \ mathrm {sys} $ mag（对应于$ 143 \ pm3 $ 3 $ kpc）。
We determine three independent Population II distance moduli to the Fornax dwarf spheroidal (dSph) galaxy, using wide-field, ground-based $VI$ imaging acquired with the Magellan-Baade telescope at Las Campanas Observatory. After subtracting foreground stars using Gaia EDR3 proper motions, we measure an $I$-band tip of the red giant branch (TRGB) magnitude of $I_0^\mathrm{TRGB} = 16.753 \pm 0.03_\mathrm{stat} \pm 0.037_\mathrm{sys}$ mag, with a calibration based in the LMC giving a distance modulus of $μ_0^\mathrm{TRGB} = 20.80 \pm 0.037_\mathrm{stat} \pm 0.057_\mathrm{sys}$ mag. We determine an RR Lyrae (RRL) distance from template mean magnitudes, with periods adopted from the literature. Adopting a Gaia DR2 calibration of first overtone RRL period-luminosity and period-Wesenheit relations, we find $μ_0^\mathrm{PLZ} = 20.74 \pm 0.01_\mathrm{stat} \pm 0.12_\mathrm{sys}$ mag and $μ_0^\mathrm{PWZ} = 20.68 \pm 0.02_\mathrm{stat} \pm 0.07_\mathrm{sys}$ mag. Finally, we determine a distance from Fornax's horizontal branch (HB) and two galactic globular cluster calibrators, giving $μ_0^\mathrm{HB} = 20.83 \pm 0.03_\mathrm{stat} \pm 0.09_\mathrm{sys}$ mag. These distances are each derived from homogeneous IMACS photometry, are anchored to independent geometric zero-points, and utilize different classes of stars. We therefore average over independent uncertainties and report the combined distance modulus $\langle μ_0\rangle = 20.770 \pm 0.042_\mathrm{stat} \pm 0.024_\mathrm{sys}$ mag (corresponding to a distance of $143\pm3$ kpc).
