Mapping the Intergalactic Medium Using Lyman-Alpha Data and Persistent Homology

• Activity Number: 485
• Type: Contributed
• Date/Time: Wednesday, August 7, 2013 : 8:30 AM to 10:20 AM
• Sponsor: Section on Physical and Engineering Sciences
• Author(s): Jessi Cisewski*+ and Christopher R. Genovese and Larry Wasserman and Rupert Croft and Peter Freeman and Melih Özbek
• Companies: Carnegie Mellon University and Carnegie Mellon University and Carnegie Mellon University and Carnegie Mellon University and Carnegie Mellon University and Carnegie Mellon University
• Keywords: astrostatistics ; local regression ; computational topology ; persistent homology ; local polynomial smoothing

Abstract

Light from extremely bright objects from the early Universe (quasars) has traveled through the intergalactic medium (IGM) to reach us, and leaves an imprint of some properties of the IGM on its spectrum. There is a particular imprint of which cosmologists are familiar, dubbed the Lyman-alpha Forest. From this imprint, we can infer the density of neutral hydrogen along the line of sight from us to the quasar.

With cosmological simulation output, we develop a methodology using local polynomial smoothing to model the IGM. I will briefly describe the modeling methodology, but focus on how to analyze the adequacy of the modeling procedure and discuss some of the issues faced when modeling the real data from SDSS - DR9. Finally, describing the topological features of the IGM can aid in our understanding of the large-scale structure of the Universe along with providing a framework for comparing cosmological simulation output with real data beyond the standard measures. Accessing important topological features of data can be accomplished with persistent homology - I will introduce persistent homology, and describe an example of how it can be used in cosmology.