Precision Measures of the Dark Sector

Dodelson博士将专注于理解暗物质和暗能量的两个核心问题：弱引力透镜测量中的选择偏差，以及探测暗物质粒子湮灭时产生的光子。星系调查只能包括大于给定大小和视亮度的天体。当来自背景星系的光在到达我们的途中接近一个密集区域时，它的光被弯曲（“透镜”），因此它看起来比其他情况更亮、更大。这种偏差导致了一种错觉，在天空的同一部分，遥远的暗星系和附近的物质聚集在一起。初步计算表明，选择偏差可能会使一些测量量改变多达10%。Dodelson博士将进行更详细的计算，包括为暗能量调查准备的宇宙流体动力学模拟分析，以及如何将星系图像与斯隆数字巡天中的恒星图像区分开来的研究。他的目标是了解选择偏差可能如何影响未来用弱透镜测量暗能量的大型调查，并开发出将其最小化的分析方法。目前关于构成暗物质的粒子的观点预测它们应该有有限的寿命，因此像费米这样的伽马射线望远镜可以探测到暗物质粒子湮灭时产生的数千个光子。然而，来自我们银河系和活跃星系核的伽马射线的“背景”要亮得多。Dodelson博士将探索从背景中提取暗物质信号的方法。研究生将通过参与研究而得到训练。Dodelson博士在包括斯隆数字巡天、暗能量巡天和超新星加速探测器在内的大型合作项目中发挥着重要作用，这些项目旨在限制产生暗能量的基本物理学。

Dr Dodelson will focus on two issues central to understanding dark matter and dark energy: selection bias in measurements of weak gravitational lensing, and detecting the photons produced as dark matter particles annihilate. Galaxy surveys can include only objects above a given size and apparent brightness. When light from a background galaxy passes close to a dense region on its way to us, its light is bent ('lensed') so that it appears brighter and larger than otherwise. This bias introduces an illusory concentration of faint distant galaxies in the same parts of the sky as nearby concentrations of matter. A preliminary calculation shows that selection bias could change some measured quantities by as much as 10%. Dr Dodelson will undertake more detailed calculations, including an analysis of cosmological hydrodynamic simulations prepared for the Dark Energy Survey, and studies of how galaxy images are distinguished from those of stars in the Sloan Digital Sky Survey. His aim is to understand how selection bias is likely to affect future large surveys to measure dark energy with weak lensing, and to develop analysis methods that minimize it. Current ideas about the particles making up the dark matter predict that they should have finite lifetimes, so that gamma ray telescopes such as Fermi would detect thousands of photons produced when dark matter particles annihilate. However, the 'background' of gamma rays from our own Milky Way, and from the active nuclei of galaxies, is far brighter. Dr Dodelson will explore methods to extract the dark matter signal from the background.A graduate student will be trained by participating in the research. Dr Dodelson plays a significant role in large collaborations including the Sloan Digital Sky Survey, the Dark Energy Survey, and the SuperNova Acceleration Probe, which aim at constraining the fundamental physics that gives rise to the dark energy.