.. _HeII_to_HI_column_density_ratio:

HeII-to-HI column density ratio
===============================

**Field names**: 
"HeII_to_HI_column_density_ratio", "eta"

**Units**: 


**Remarks**: 


**Required fields**: 
"redshift"


    
Data
^^^^

.. image:: ../plots/HeII_to_HI_column_density_ratio.png
   :height: 200pt

**Data sources**

|Syphers & Shull 2014|

.. |Syphers & Shull 2014| raw:: html

   <a href="https://iopscience.iop.org/article/10.1088/0004-637X/784/1/42" target="_blank">Syphers & Shull 2014</a>