Damped and Sub-damped Lyman-alpha Absorbers: What Are They, and What Do They Tell Us About Galaxy Evolution?

该奖项由2009年美国复苏和再投资法案(公法111-5)资助。库尔卡尔尼博士将通过观察更远的明亮类星体光谱中的吸收线来研究星系之间和新生星系周围的气体。一般来说，最稠密的气体，在受阻的莱曼-阿尔法吸收体中，已经在形成恒星。如果这些吸收体代表年轻的星系，我们预计重元素的丰度将从较低的值上升到大致相当于今天的太阳水平，因为垂死的恒星会将这些元素返回到气体中。相反，大多数这样的气云都是贫金属的。库尔卡尼博士和她的合作者已经证明，密度稍低的亚阻尼莱曼-阿尔法吸收体确实会像预期的那样，随着时间的推移变得更加富含金属。这表明，许多恒星形成活动都发生在这些密度较低的星云中。库尔卡尼博士将对阻尼型和亚阻尼型莱曼-阿尔法吸振器进行进一步的研究。她将以更大的样本为样本，阐明低金属含量系统和高金属含量系统之间的物理和化学差异。使用双子座和凯克望远镜的自适应光学技术，她将获得它们在近红外中恒星形成区域的深度图像。与欧洲的合作者一起，她将在甚大望远镜上获得空间分辨光谱，以追踪年轻恒星电离的气体的运动，并检查气体性质的梯度。利用麦哲伦望远镜对双星体类星体和引力透镜类星体进行光谱分析将探测吸收气体的空间范围。一名研究生将通过参与这项研究进行培训。Kulkarni博士将继续在当地学校和组织进行外展讲座，并在校园天文台举行公众观察会。她在指导来自代表性不足群体的学生进行研究方面有着很好的记录，她将继续这样做。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr Kulkarni will study the gas between galaxies and around nascent galaxies by observing its absorption lines in the spectra of more distant bright quasars. Generally, the densest gas, in the damped Lyman-alpha absorbers, is already forming stars. If these absorbers represented young galaxies, we would expect the abundance of heavy elements to rise from a low value towards roughly the solar levels at the present day, as dying stars return these elements to the gas. Instead, most such gas clouds are metal-poor. Dr Kulkarni and her collaborators have shown that 'sub-damped Lyman-alpha absorbers', of slightly lower density, do become more metal-rich over time as expected. This suggests that much star-forming activity happens in these less-dense clouds. Dr Kulkarni will conduct further studies of both damped and sub-damped Lyman-alpha absorbers. She will take spectra for a larger sample, to elucidate the physical and chemical differences between systems of low and high metal content. Using adaptive-optics techniques at the Gemini and Keck telescopes, she will obtain deep images of their star-forming regions in the near infrared. With European collaborators, she will obtain spatially resolved spectroscopy at the Very Large Telescope, to trace the motions of gas ionized by the young stars and examine gradients in gas properties. Spectroscopy of binary quasars and gravitationally lensed quasars with the Magellan telescopes will probe the spatial extent of the absorbing gas.A graduate student will be trained by participating in the research. Dr Kulkarni will continue her outreach talks at local schools and organizations, and public observing sessions at the campus observatory. She has a strong record of mentoring students from under-represented groups in research, which she will continue.