<p>The <a href="http://en.wikipedia.org/wiki/Lyman-alpha_forest" rel="noreferrer">Lyman-alpha forest</a> is an interesting feature found in the spectra of sufficiently distant objects. This series of absorption lines extends over a range of frequencies, and are a result of the <a href="http://en.wikipedia.org/wiki/Lyman-alpha_forest" rel="noreferrer">Lyman-alpha electron transition</a> of neutral hydrogen in between the source and the observer. </p>

<p><img src="https://i.sstatic.net/ahImV.gif" alt="Lyman-alpha forest"></p>

<p>My question is: 
What information can be gleaned about the universe from this spectral feature?  In other words, what areas of research use the Lyman-alpha forest as a tool, instead of seeing it as noise? </p>

CC BY-SA 3.0
2014-03-15T20:29:01.110Z
The Lyman alpha forest encodes the neutral fraction of the density of hydrogen along the line of sight convolved by its temperature and Doppler shifted by its peculiar velocity. Hence it allows you to study all three fields, which is extremely useful, e.g. to understand the physical state of the intergalactic medium, its kinematics, it geometry.
chris
CC BY-SA 3.0
2014-03-16T12:47:03.773Z
@chris Great comment. I'd encourage you to make this into an answer.
astromax
<spectra>
What is the Lyman Alpha forest Used For?
astromax
# What is the Lyman Alpha forest Used For?

(Asked by: username_0 on 2013-10-16)

The [Lyman-alpha forest](http://en.wikipedia.org/wiki/Lyman-alpha_forest) is an interesting feature found in the spectra of sufficiently distant objects. This series of absorption lines extends over a range of frequencies, and are a result of the [Lyman-alpha electron transition](http://en.wikipedia.org/wiki/Lyman-alpha_forest) of neutral hydrogen in between the source and the observer.

![Lyman-alpha forest](https://i.sstatic.net/ahImV.gif)

My question is:
What information can be gleaned about the universe from this spectral feature? In other words, what areas of research use the Lyman-alpha forest as a tool, instead of seeing it as noise?

**Tags:** spectra
> **Comments:**
> **username_1**: The Lyman alpha forest encodes the neutral fraction of the density of hydrogen along the line of sight convolved by its temperature and Doppler shifted by its peculiar velocity. Hence it allows you to study all three fields, which is extremely useful, e.g. to understand the physical state of the intergalactic medium, its kinematics, it geometry.  
> **username_0**: @chris Great comment. I'd encourage you to make this into an answer.  

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## 0 answers

