A new method for measuring the global magnetic field structure of the Galactic plane is presented. We have determined the near-infrared polarization of field stars around 52 Cepheids found in recent surveys toward the Galactic plane. The Cepheids are located at the galactic longitudes $-10^{\circ}\leq \, l\, \leq +10.5^{\circ}$ and latitudes $-0.22^{\circ}\leq \, l\, \leq +0.45^{\circ}$, and their distances are mainly in the range of 10 to 15 kpc from the Sun. Simple classification of the sightlines is made with the polarization behavior vs. $H-K_{\mathrm S}$ color of field stars, and typical examples of three types are presented. Then, division of the field stars in each line of sight into (a) foreground, (b) bulge, and (c) background is made with the $Gaia$ DR2 catalog, the peak of the $H-K_{\mathrm S}$ color histogram, and $H-K_{\mathrm S}$ colors consistent with the distance of the Cepheid in the center, respectively. Differential analysis between them enables us to examine the magnetic field structure more definitely than just relying on the $H-K_{\mathrm S}$ color difference. In one line of sight, the magnetic field is nearly parallel to the Galactic plane and well aligned all the way from the Sun to the Cepheid position on the other side of the Galactic center. Contrary to our preconceived ideas, however, sightlines having such well-aligned magnetic fields in the Galactic plane are rather small in number. At least 36 Cepheid fields indicate random magnetic field components are significant. Two Cepheid fields indicate that the magnetic field orientation changes more than 45 in the line of sight. The polarization increase per color change $P$/ ($H-K_{\mathrm S}$) varies from region to region, reflecting the change in the ratio of the magnetic field strength and the turbulence strength.

中文翻译：

---

星际极化微分分析的银道面磁场结构

提出了一种测量银河平面全局磁场结构的新方法。我们已经确定了在最近对银河平面的调查中发现的 52 颗造父变星周围的场星的近红外偏振。造父变星位于银河经度 $-10^{\circ}\leq \, l\, \leq +10.5^{\circ}$ 和纬度 $-0.22^{\circ}\leq \, l\, \leq +0.45^{\circ}$，它们与太阳的距离主要在 10 到 15 kpc 的范围内。用场星的极化行为与$H-K_{\mathrm S}$颜色对视线进行了简单的分类，并给出了三​​种类型的典型例子。然后，将每条视线中的场星划分为（a）前景、（b）凸起和（c）背景，这是用 $Gaia$ DR2 目录，$H-K_{\mathrm S }$ 颜色直方图，和 $H-K_{\mathrm S}$ 颜色分别与中心造父变星的距离一致。它们之间的差异分析使我们能够比仅仅依靠 $H-K_{\mathrm S}$ 色差更明确地检查磁场结构。在一条视线中，磁场几乎平行于银河平面，并且从太阳到银河中心另一侧的造父变星位置一直很好地对齐。然而，与我们先入为主的想法相反，在银道平面中具有这种对齐良好磁场的视线数量相当少。至少 36 个造父变星场表明随机磁场分量很重要。两个造父变星场表明磁场方向在视线内变化超过 45。