Cosmology Seminar

Extremely Low-Luminosity Galaxies in the Early Universe: New Horizons for Hubble, Spitzer, and the James Webb 
By combining the power of gravitational lensing magnification from massive galaxy clusters with long exposures from the Hubble and Spitzer Space Telescopes, the Hubble Frontier Fields initiative allows us to look fainter into the universe than ever before. In so doing, the campaign provides us with our first-ever direct probe into the prevalence of extremely low luminosity galaxies in the early universe, while simultaneously providing us with a high spatial resolution view of the same galaxies. Interestingly enough, not only does this new high resolution view suggest that many ultra-faint galaxies have sizes similar to that of super star clusters, i.e., 30-150 parsecs, but also this same view is essential to obtaining a systematics-free answer to the prevalence of these same galaxies and their ionizing emissivities. The purpose of my presentation is to describe not only the sizes, structure, and other properties the community is discovering for extremely low luminosity galaxies (100-1000 times fainter than L*), but also current efforts to probe the galaxy luminosity function into the same regime.