Virtual Department Colloquium: Tues Dec 8, 2020 - The Rise of Galaxies in the Early Universe

Event Date: 

Tuesday, December 8, 2020 - 4:00pm

Event Location: 

  • Zoom
  • Physics Department Colloquium
The Rise of Galaxies in the Early Universe
Steven Finkelstein, UT Austin
 
Reionization was the last major phase transition of the universe, and both the time evolution and spatial variation of this process encode key information about the onset of luminous objects in the universe. While we think that massive stars within star-forming galaxies provide the needed ionizing photons, the observed escape fractions of these photons may be too low to complete reionization when combined with typical assumptions. We have devised a new semi-empirical model which resolves this tension by using simulation-motivated escape fractions, where the smallest halos have the highest escape fractions, leading to a successful completion of reionization by z=5.5 with low (<5%) average ionizing photon escape fractions. Our model makes a number of testable predictions, including: 1) AGNs contribute non-negligibly to the end of reionization, 2) the neutral fraction at z~7 is only ~20%, and 3) significant star-formation must be occurring at z~9-10. I will focus on observational results from our group at UT Austin testing all of these assumptions, including results from ultra-deep Keck spectroscopy for Lyman-alpha emission at z~7-10, and the discovery of several remarkably bright galaxy candidates at z > 9. I'll conclude by discussing our JWST Early Release Science program, CEERS, outlining the wealth of publicly available imaging and spectroscopy we will be obtaining, and our rapid delivery schedule of reduced data and catalogs.
 
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Meeting ID: 842 1723 4934
Passcode: 153690