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SUMMARY:Solving Reionization with Resolved Lyman-alpha - Rohan Naidu (CfA)
  
DTSTART:20220204T113000Z
DTEND:20220204T123000Z
UID:TALK166012@talks.cam.ac.uk
CONTACT:Martin Haehnelt
DESCRIPTION:The most pressing questions around Reionization -- e.g.\, whet
 her its protagonists were a handful of bright galaxies (``the oligarchs") 
 or numerous ultra-faint sources (``democratic reionization") --  hinge on 
 the unknown ionizing photon escape fractions (LyC fesc) of star-forming ga
 laxies. Efforts to understand the physics and statistics of LyC fesc have 
 been stymied by our inability to construct pure samples of LyC leakers vs.
  non-leakers due to stochastic sightline effects. I will argue high-resolu
 tion Lyman-alpha (LyA) spectroscopy is the panacea to these issues. Using 
 the X-SHOOTER LyA survey at z~2 (XLSz2) I will present clean stacks of lea
 kers vs. non-leakers that show dramatic differences across ~1000-8000A -- 
 these differences clarify how/why ionizing photons escape and identify the
  features that can be studied at z>6 to constrain fesc (e.g.\, MgII\, O32\
 , HeII). The leakers constitute half our survey\, and have escape fraction
 s ~50%. Building on these results\, I will present a LyA-based framework f
 or the ionizing emissivity from z~2-8 that both explains the puzzling flat
 ness of the emissivity at z~2-6 as well as rapid reionization between z~6-
 8. I will end by previewing two Cycle 1 JWST programs I am leading -- thes
 e programs examine ionized bubbles towards the beginning and end of reioni
 zation\, and will produce some of the deepest grism pointings in Cycle 1 t
 o enable a variety of z~1-9 science.\n
LOCATION:via zoom 
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