Along with the mid-cycle proposal template is attached a letter from my faculty adviser since I'm a student PI.-1774872430Assigned ID: 1547
----- Attempting Submission 1 (Fri Sep 29 22:15:44 GMT 2017) -----
HST Phase I Proposal 1547 (Midcycle_proposal.apt) successfully submitted.
Receipt: # 1547-1Resubmission: a) Removed postarg offsets, now using UVIS2-C1K1C-CTE aperture, b) Added an ORIENT 5-345 to avoid bright nearby star, c) Slight postarg offsets to provide some large scale dithering293655055----- Attempting Submission 1 (Mon Dec 04 16:43:24 GMT 2017) -----
----- Attempting Submission 2 (Fri Dec 08 07:54:25 GMT 2017) -----Confirming Extreme Lyman Continuum Emission in a z=3.27 Star-Forming GalaxyIdentifying the drivers of cosmic reionization ("Lyman Continuum (LyC)" leakers) is an open frontier in observational cosmology. Star-forming galaxies are leading candidates, provided their critical parameter "f_esc" (the fraction of ionizing photons escaping to the IGM) is found to exceed 10-20%. Since the opaque IGM precludes direct observations of f_esc at z>6, extensive searches for low-z LyC leakers have been mounted. These sources, however, have proven notoriously elusive--only three have been found at z>0.5. We propose to confirm LyC emission from a new, promising candidate (GS15601) at z_spec=3.2705+/-0.0007, which would be the highest redshift and most extreme LyC leaker so far. GS15601 was detected in deep F336W WFC3/UVIS imaging in our HDUV survey which directly probes LyC emission at z>3. Detailed simulations show that its high F336W LyC flux implies an extreme LyC output, a very high f_esc>50%, and an almost transparent IGM line of sight. Unfortunately, GS15601 was imaged by a detector region with poor charge transfer efficiency (CTE)--its flux is robustly recovered but S/N is lost. Given the potentially extraordinary physical situation in GS15601, and the systematic uncertainties introduced by CTE loss correction and cosmic ray cleaning, we seek independent confirmation of this high LyC flux measurement with a small amount of additional F336W data. If confirmed, GS15601 will give us the rare chance to study the physics of LyC escape and calibrate indirect methods of inferring f_esc from UV and optical lines--these indirect methods are our only hope of measuring f_esc at z>6 with JWST and solving the puzzle of cosmic reionization.This program aims to obtain a robust F336W flux measurement for a z=3.27 galaxy. The current flux we measure is significantly affected by charge transfer inefficiency. In this program we will place GS15601 close to the edge of the detector (15" from the UVIS2 pointing position), hence minimizing charge transfer and providing an independent, clean measurement. Additionally, we will flash the detector to the required 12 electron/pixel level before every exposure in order to produce a uniform image that can be appropriately CTE corrected over the full WFC3/UVIS field-of-view.
Pointing: we use the UVIS2 pointing position with an additional y=-15" POSTARG offset in order to put the primary target close to the readout and minimize the CTE losses.
Orbit Structure: We propose the following structure: three visits, the first two have two orbits each (4 exposures) and the final visit has a single orbit (2 exposures).
Dithering: The two orbit visits use the standard 4point UVIS dither box, while the 1 orbit visit uses a two point linear dither. Between each visit, we apply a small POSTARG offset to step across the UVIS chip gap and improve the data quality.
Post-Flash:
We use an 8 electron post-flash background to reach the 12e- level at each readout to improve the CTE.
ACS Parallels:
In parallel to our WFC3/UVIS exposures, we will take ACS/WFC3 parallel imaging in F435W.
Orients: No constraints are set on the orients of these observations, but ideally the visit should be scheduled close enough in time to have a similar orient for each.Galaxies and the IGMCosmology3falsefalsefalsefalsefalsefalseSUPPORTEDGALAXYSTARBURSTJ2000J2000WFC3/UVISImagingNoNoF336WACS/WFCImagingNoNoF435WPOS-TARGDITHER0.173LINE0.112falsefalse81.785423.884WFC3-UVIS-DITHER-BOX1falsePOS-TARGDITHER0.145LINEfalsefalse246.84WFC3-UVIS-DITHER-LINE2falseHst Same orient constraint links visits (01 02 03)The scheduling data was generated by CASM 25.2.CASM was run in Phase II mode.C:\Users\rpn3\AppData\Local\Temp\OPVisit3652254923385863987.xml(Tic-Visit
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