Measuring Mass Distributions in Moderate-Redshift Galaxies Through Gravitational Lensing

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。Fassnacht博士将使用强大的引力透镜效应，即光线在接近大质量物体时发生弯曲，来研究大质量椭圆星系的质量分布，探索宇宙年龄大约是现在年龄一半的时代。前景“透镜”星系中恒星的速度色散将使用凯克望远镜上的多缝光谱仪在光学和近红外波段测量。未确定的缝隙将用于测量天空中附近星系的红移，以研究透镜周围的任何星系群或星团。哈勃太空望远镜的图像将用于测量光线从中央透镜经过100kpc或更多的星系的弱透镜畸变，探测透镜星系的巨大暗晕。最后，凯克望远镜上的自适应光学成像将用于寻找透镜星系的微弱伴星。图像的亮度比通常与平滑的椭圆透镜所期望的不同，这表明可能存在伴星。Fassnacht博士已经用这种技术找到了一个透镜星系的微弱伴星。一名研究生和一名本科生将参与研究。Fassnacht博士将继续他的公共宣传讲座项目，他将向加州大学戴维斯分校现有的高中生项目介绍天文学。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Dr Fassnacht will use strong gravitational lensing, the bending of light as it passes close to a massive object, to study the mass distributions of massive elliptical galaxies, probing back to times when the cosmos was roughly half as old as it is now. The velocity dispersion of the stars in the foreground 'lensing' galaxy will be measured using multislit spectrographs on the Keck telescopes in the optical and in the near-infrared. Uncommitted slits will be used to measure redshifts of galaxies lying nearby on the sky, to study any group or cluster surrounding the lens. Hubble Space Telescope images will be used to measure the weak lensing distortions for galaxies whose light passes 100kpc or more from the central lens, probing the massive dark halo of the lensing galaxy. Finally, adaptive optics imaging on the Keck telescopes will be used to search for faint companions to the lens galaxy. Brightness ratios for the images are often discrepant from what would be expected for a smooth elliptical lens, suggesting that companions may be present. Dr Fassnacht has already used this technique to find a faint companion to one lens galaxy. A graduate student and undergraduate researchers will participate in the research. Dr Fassnacht will continue his program of public-outreach talks, and he will introduce astronomy to an existing program at UC Davis for high school students.