Spectroscopy of Galaxies in the Reionization Era

Prof. Daniel Stark (Arizona)
May 15, 2018 - 4:00pm


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 have 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 and are proving challenging to interpret, owing in large part to our incomplete knowledge of low metallicity massive stellar populations.   In this talk, I will review the latest progress in our understanding of the galaxies in the first billion years of cosmic history and discuss remaining challenges that must be addressed in advance of JWST.