Extremely Low-Luminosity Galaxies in the Early Universe: New Horizons for Hubble, Spitzer, and James Webb

Rychard Bouwens
May 15, 2017 - 4:00pm


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 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 presentaton 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.