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Jessi Cisewski - Carnegie Mellon University

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Far away and just as long ago: Visualizing the Intergalactic Medium using the Lyman-alpha forest
27 February 2014 from 4:00 PM to 5:00 PM
201 Thomas Building
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Light we observe from 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 distribution of neutral hydrogen along the line

of sight from us to the quasar.  The Sloan Digital Sky Survey Data Release

9 (SDSS – DR9) produced over 54,000 quasar spectra that can be used for

analysis of the Lyman-alpha forest and, thus, aid cosmologists in further

understanding the IGM along with revealing or corroborating other

properties of the Universe.


              With cosmological simulation output, we develop a methodology using local

polynomial smoothing to map the IGM.  I will describe the modeling

methodology, how to analyze the adequacy of the modeling procedure and

discuss some of the issues faced due to the design of the data.  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 this setting.

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