Hunting E+A Galaxies Through SDSS-MaNGA Integral Field Spectroscopy     

The study of galaxy evolution is an ongoing issue within the astrophysical realm. The process of quenching-- the cessation of star formation-- is still a process that astronomers do not fully understand, meanwhile the steps leading up to this process are even more of a mystery.  The evolutionary path of these massive stellar populations becomes a labyrinth of theory when we introduce the concept of the "Green Valley". First described by Bell et al. (2003), the Green Valley is a region on the galaxy color-magnitude diagram that lies between the Blue Cloud (star-forming galaxies) and the Red Sequence (quenched galaxies). While they are relatively small in number, these peculiar standouts occur often enough to be considered more than just a mere aberration. Figure 1 is a density map of the all galaxy color-mass diagram found in Schawinski et al. (2014), here one can see a visual representation of the green valley. While there are several types of green valley galaxies, our study focuses on E+A galaxies. Simply described as "post starburst galaxies"  in Dressler and Gunn (1987) these odd galaxies simultaneously host an old stellar population-- characteristic of ellipticals-- and a large amount of A-type stars (indicating recent cessation of star formation). This unusual blend of old and young is the essence of the Green Valley, the study of which may very well hold the key to unraveling the mystery of galaxy evolution. The question that we really want to answer is whether these E+A's are simply a transitory state between star forming and quiescent galaxies, or if they are the result of a more complex evolutionary process.