Project ALCATRAZ: Archival Lyman-Continuum and Theoretical Reionization Analysis vs. z: Where, When, How & How Much does LyC Escape?
Abstract
We propose a systematic Archival study of the best available UV images: the WFC3 Early Release Science {ERS} data and, as a check, also the HUDF. Each was imaged in 3 WFC3 UV filters + 7-9 ACS and WFC3/IR filters. SED fits provide photo-z, luminosity, stellar mass, age, SFR, and extinction estimates. Stacking the 2-45 orbit native depth for 100's of objects will reach UV-depths of 100's-1000's of orbits, paying careful attention to systematics. Our main goal is to outline where, when, how and how much Lyman continuum {LyC} escapes from both galaxies and AGN in the epoch z=2 to z=7-11. Detailed science goals are:1. Where does LyC escape, and for which classes of objects? We will study escaping LyC vs. galaxy luminosity, mass, age, SFR, and extinction, and for {weak} AGN. 2. When did LyC escape, and how did this vary with epoch? Available spectroscopic redshifts and the 10-12-filter photo-z probability distribution will be used to maximize each subsample, masking out all foreground interlopers.3. How does LyC escape? Is it mostly via direct unobscured lines of sight? Or can it escape dusty star-forming galaxies and/or dusty AGN with outflows, but be scattered in our direction off electron and/or dust clouds? 4. How much escaping LyC can we measure reliably? Preliminary WFC3 ERS results suggest a LyC flux for galaxies {and also some AGN} at z=2.45-4.2 of 28.4-29.5 mag/arcsec^2 {5.0-2.0-sigma}, in line with our scattering predictions. Does any hard LyC escape below restframe 200-300 A from z=7-11 candidates along a few lucky unobscured lines-of-sight?ALCATRAZ can and must be done now to constrain the processes that started and maintained cosmic reionization.
- Publication:
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HST Proposal
- Pub Date:
- October 2014
- Bibcode:
- 2014hst..prop13877W