Exploring the Galaxy: 3-Dimensional Structure and Stellar Streams

研究人员利用Pan-STARRS-1对近10亿颗恒星的调查（PS1）来绘制银河系中的尘埃和气体。根据这些恒星的颜色，研究人员开创了一种方法，可以非常精确地测量银河系旋臂中的尘埃和气体。尘埃使星光变红，原因和日落变红是一样的。天文学家使用这张地图来确定与各种物体的距离，并修正尘埃对数据的影响。研究人员将扩展他们的第一个工作，在北方天空，使用一个新的南方天空调查来绘制整个星系的三维结构。研究人员有一个计划，通过一种新的平均数据的方法来提高他们地图的准确性。所有的地图都将公开发布，并将为三维变红估计、恒星流搜索和其他银河系结构工作提供一个具有巨大价值的遗留数据集。它们将通过拥有超过1000万独立用户的世界范围望远镜接口向公众开放。在绘制第一代3-D尘埃图的过程中，研究人员发现了技术上的改进，比如空间正则化，这将提高地图的定量可靠性。而不是单独计算地图的每个像素，下一个地图将结合来自相邻像素的信息来稳定拟合，并允许更小的像素（角度和距离）和更低的噪声。新地图还将纳入观测选择函数和银河系先验的详细信息，从而有可能估计出每个体积元素中每种类型的恒星数量。包含来自盖亚的适当运动和视差将稳定三维拟合并增加地图的保真度。及时的数据发布刺激了知识的进步，研究者有一个强有力的数据发布记录，可以追溯到第一张尘埃地图。第一代3-D地图已经导致分子云距离目录的发布。综合（沿着每条视线）地图已经与基于排放的地图进行了测试，结果发现两者非常吻合。本文提出的改进的“第二代”尘埃和恒星图将是对银河系结构的有力探测，并可能导致发现新的潮汐流、盘翘曲和其他有助于我们理解银河系动力学的特征。此外，这些地图将为直接计算6-D辐射场（每个地方、每个方向、每个能量的辐射量）的长期目标提供基础。

The investigators have used the Pan-STARRS-1 survey (PS1) of nearly 1 billion stars to map the dust and gas in our galaxy. Based on the colors of these stars, the investigators have pioneered a method to very accurately measure the dust and gas in the spiral arms of our galaxy. Dust reddens starlight, for the same reason that sunsets are red. Astronomers use this map to determine distances to various objects, and to correct for the effects of dust on their data. The investigators will expand their first work, over the northern sky, using a new southern sky survey to map the 3-dimensional (3-D) structure of the entire galaxy. The investigator has a plan for improving the accuracy of their map, through averaging the data in a new way.All maps will be publicly released and will provide a legacy dataset of enormous value for 3-D reddening estimates, stellar stream searches, and other Galactic structure work. They will be available to the general public via the World-Wide Telescope interface, which has over 10 million unique users.In the process of creating the first-generation 3-D dust map the investigator has identified technical improvements, such as spatial regularization, that would enhance the quantitative reliability of the map. Rather than computing each pixel of the map independently, the next map will combine information from neighboring pixels to stabilize the fit and allow smaller pixels (both angle and distance) with lower noise. The new map will also incorporate detailed information on the observational selection function and Galactic priors to make possible an estimate of the number of stars of every type in every volume element. Inclusion of proper motions and parallaxes from Gaia will stabilize the 3-D fit and increase the fidelity of the map.Timely data releases spur the advancement of knowledge, and the investigator has a strong record of data releases date back to the first dust maps. The first-generation 3-D map has already resulted in the release of a molecular cloud distance catalog. The integrated (along each line of sight) map has been tested against emission-based maps and found to agree well. The improved "second-generation" maps of dust and stars proposed herein will be a powerful probe of Galactic structure, and may lead to discoveries of new tidal streams, disk warps, and other features that help us understand Galactic dynamics. Additionally these maps will provide a foundation for the longer-term goal of a direct calculation of the 6-D radiation field (amount of radiation at every place, in every direction, at every energy).