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Emission Expedition: A Spectral Study of 800,000 Galaxies

Presentation #241.12 in the session Evolution of Galaxies — iPoster Session.

Published onJun 29, 2022
Emission Expedition: A Spectral Study of 800,000 Galaxies

Star forming regions and AGN are both strongly associated with emission lines. What can a large sample study of emission lines in galactic spectra tell us about the star formation and AGN history of the universe? We use data from the Sloan Digital Sky Survey (SDSS) to observe changes in the number of emission line galaxies, star forming galaxies, and AGN with redshift. We obtained the spectra for close to 800,000 galaxies out to a redshift of about z = 0.6 from Data Release 16 of the SDSS. This gives a sample size large enough to draw conclusions about the rate of change of galactic properties with redshift. We charted the fraction of emission line galaxies using spectral lines in the visible region, created BPT (Baldwin, Phillips, and Terlevich) diagrams to represent the relative changes in star forming galaxies and AGN, and calculated the change in average star formation rate with redshift. As we look farther in redshift, the fraction of emission line galaxies decreases, the average star formation rate increases, and the ratio of star forming galaxies to AGN decreases. This may indicate that higher star formation rates in the past are driven by a smaller fraction of galaxies.

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