Astronomy & Astrophysics Colloquium: Dan Stark (Univ. of Arizona) “Galaxies in the Reionization Era”

3:30–4:30 pm ERC 161

Over the past decade, deep infrared images have pushed the cosmic frontier back to just 500 million years after the Big Bang, delivering the first large sample of galaxies at redshifts 7<z<10.  Sometime in this redshift window the hydrogen in the intergalactic medium transitioned from mostly neutral to ionized.  The emergence of the first detailed spectra of z>7 galaxies from ALMA, Magellan, and Keck has begun to sharpen our understanding of this reionization process while also providing a glimpse of the physical nature of early galaxies.  The spectral features we are detecting at z>7 are unlike what has been seen at lower redshifts, hinting at a population of low mass galaxies undergoing frequent bursts of star formation.  Surveys at lower redshift have begun to reveal insight into the ionizing efficiency of this population of low mass galaxies, providing quantitative constraints on the production and escape of ionizing radiation. In this talk, I will review the latest in observational efforts to understand galaxies in the reionization-era and discuss remaining challenges that must be addressed in advance of JWST.  

Event Type


Oct 9