.. _spectrum_Halpha:

Spectrum Halpha Plot
====================

.. figure:: spectra_Halpha.png
   :scale: 50 %
   :alt: spectrm Halpha

   A three-dimensional embedding of the main sample of galaxy spectra
   from the Sloan Digital Sky Survey (approximately 675,000 spectra
   observed in 3750 dimensions). Colors in the above figure indicate
   the strength of Hydrogen alpha emission, a very nonlinear feature
   which requires dozens of dimensions to be captured in a linear embedding.