18126( 2) - 05-Aug-2025 16:01:14 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18126 Version: 2 Check-in Time: 05-Aug-2025 16:01:14 STScI Edit Number: 0 Title Efficient selection of Lyman Continuum emitters at z > 3 ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Alexander Beckett Space Telescope Science Institute Y CoI: Dr. Marc Rafelski Space Telescope Science Institute Y CoI: Prof. Claudia Scarlata University of Minnesota - Twin Cities N CoI: Dr. Ilias Goovaerts Space Telescope Science Institute N CoI: Dr. Nimish P. Hathi Space Telescope Science Institute N CoI: Dr. Keunho J. Kim California Institute of Technology N CoI: Prof. Matthew A. Malkan University of California - Los Angeles N CoI: Dr. Vihang Mehta California Institute of Technology N CoI: Prof. Matthew James Hayes Stockholm University N CoI: Prof. Andrew Bunker University of Oxford N CoI: Dr. Alaina L. Henry Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract Understanding which galaxies dominated the ionizing flux (Lyman continuum, LyC) that reionized the early Universe requires measuring the escape fraction of galaxies during that epoch. This cannot be done directly, so instead we need to use indirect indicators calibrated on galaxies observed shortly after reionization. The Parallel Ionizing Emissivity (PIE) survey is an ongoing effort to address this by detecting over 400 galaxies across ~50 independent fields that can be stacked to measure how LyC emission varies with galaxy properties. This survey uses F336W imaging to probe pure LyC at 3.13 orbits of F336W data are missing one of these bands, so cannot be used. Therefore, we propose a very small investment of WFC3 imaging to complement 40 orbits of existing data in these fields. These observations will allow us to efficiently detect dropout galaxies and thereby add over 100 galaxies at 3.13 orbits of F336W data are missing one of the optical bands, so we cannot measure the colors required to select candidates for follow-up. This program aims to replace the missing F625W and F814W data and thereby substantially increase the number of candidate galaxies that we can target with spectroscopy. EXPOSURES: We use WFC3/UVIS observations so that we can utilize our existing pipeline to easily reduce the data and produce photometric catalogs including both the new and existing data. One orbit of F625W or F814W in each field is sufficient to match or exceed the depth of the existing observations. In order to ensure that CTE degradation does not affect our observations, we observe each field with three exposures (each of 750-800s depending on orbital visibility). These relatively long exposures allow for sufficient background to avoid the worst effects of poor CTE. We also add a small post-flash (2e-) to our F814W observations, ensuring that we exceed the recommended background levels. DITHER: We use the 'UVIS-GAP-LINE' dither pattern to cover the chip gap with two of our three exposures. This will allow reasonable cleaning of cosmic rays from the images and provide usable data at every location. This is particularly important for this program as the existing PIE data are not dithered, so do not cover the chip gap. The chip gap of the new data will be at a different orienation to that of the earlier data. Covering the chip gap in the new data ensures that we do not further restrict the available area in which there is coverage with all three filters. SPECIAL REQUIREMENTS: In order to maximize the overlap with the existing PIE data, we request ORIENT constraints. In the Phase I, we requested constraints such that at least 90% of the existing field is covered by the new observations (wherever this could be done with minimal impacts to schdeuling). This requires that the orientation of the new images matches that of the existing images to within ~15 degrees. For most of our observations these constraints can be applied and there are still large windows available during which they can be scheduled. However, for fields 52 and 54 (visits 07 and 08), this constraint leaves quite small windows for scheduling, so we remove the ORIENT constraints for these visits. ------------------------------------------------------------------------------------ 18126( 2) - 05-Aug-2025 16:01:14 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-10 UNIDENTIFIED, PARALLEL RA=08H15M31.1100S, J2000 V = 26.0 FIELD DEC=+29D40'3.50" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 2 PIE-FIELD-20 UNIDENTIFIED, PARALLEL RA=14H18M51.0371S, J2000 V = 26.0 FIELD DEC=+42D03'36.75" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 3 PIE-FIELD-24 UNIDENTIFIED, PARALLEL RA=16H07M27.1500S, J2000 V = 26.0 FIELD DEC=+32D14'1.81" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 4 PIE-FIELD-28 UNIDENTIFIED, PARALLEL RA=09H09M41.4700S, J2000 V = 26.0 FIELD DEC=+27D39'43.39" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 5 PIE-FIELD-30 UNIDENTIFIED, PARALLEL RA=07H45M47.4800S, J2000 V = 26.0 FIELD DEC=+19D22'54.40" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 6 PIE-FIELD-50 UNIDENTIFIED, PARALLEL RA=09H55M1.5040S, J2000 V = 26.0 FIELD DEC=+39D34'5.51" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 7 PIE-FIELD-52 UNIDENTIFIED, PARALLEL RA=06H27M55.9940S, J2000 V = 26.0 FIELD DEC=-50D57'10.94" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 8 PIE-FIELD-54 UNIDENTIFIED, PARALLEL RA=00H41M16.0520S, J2000 V = 26.0 FIELD DEC=-51D26'50.10" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 18126( 2) - 05-Aug-2025 16:01:14 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-GAP-LINE Pattern_Purpose MOSAIC Number_Of_Points 3 Point_Spacing 2.414 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.759 Angle_Between_Sides Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 18126( 2) - 05-Aug-2025 16:01:14 - [ 5] Visit: 01 Visit Requirements: ORIENT 1D TO 31 D; ORIENT 91D TO 121 D; ORIENT 181D TO 211 D; ORIENT 271D TO 301 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-1 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=2 1 550 S PATTERN 3 1 0 S ER see below (2331 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PIE-FIELD-10 1 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 777.0 S S TER PIE-FIELD-10 1 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 1 777.0 S S TER PIE-FIELD-10 1 WFC3/UVI ACCUM UVIS-CEN F814W 3 none none none 1 777.0 S S TER 18126( 2) - 05-Aug-2025 16:01:14 - [ 6] Visit: 02 Visit Requirements: ORIENT 68D TO 98 D; ORIENT 158D TO 188 D; ORIENT 248D TO 278 D; ORIENT 338D TO 8 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-2 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=2 1 550 S PATTERN 3 1 0 S ER see below (2349 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PIE-FIELD-20 1 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 783.0 S S TER PIE-FIELD-20 1 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 1 783.0 S S TER PIE-FIELD-20 1 WFC3/UVI ACCUM UVIS-CEN F814W 3 none none none 1 783.0 S S TER 18126( 2) - 05-Aug-2025 16:01:14 - [ 7] Visit: 03 Visit Requirements: ORIENT 73D TO 103 D; ORIENT 163D TO 193 D; ORIENT 253D TO 283 D; ORIENT 343D TO 13 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-2 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=2 1 550 S PATTERN 3 1 4 S ER see below (2337 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PIE-FIELD-24 1 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 779.0 S S TER PIE-FIELD-24 1 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 1 779.0 S S TER PIE-FIELD-24 1 WFC3/UVI ACCUM UVIS-CEN F814W 3 none none none 1 779.0 S S TER 18126( 2) - 05-Aug-2025 16:01:14 - [ 8] Visit: 04 Visit Requirements: ORIENT 101D TO 131 D; ORIENT 191D TO 221 D; ORIENT 281D TO 311 D; ORIENT 11D TO 41 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-2 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=2 1 550 S PATTERN 3 1 8 S ER see below (2331 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PIE-FIELD-28 1 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 777.0 S S TER PIE-FIELD-28 1 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 1 777.0 S S TER PIE-FIELD-28 1 WFC3/UVI ACCUM UVIS-CEN F814W 3 none none none 1 777.0 S S TER 18126( 2) - 05-Aug-2025 16:01:14 - [ 9] Visit: 05 Visit Requirements: ORIENT 90D TO 120 D; ORIENT 180D TO 210 D; ORIENT 270D TO 300 D; ORIENT 0D TO 30 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-3 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=2 1 550 S PATTERN 3 1 0 S ER see below (2325 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PIE-FIELD-30 1 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 775.0 S S TER PIE-FIELD-30 1 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 1 775.0 S S TER PIE-FIELD-30 1 WFC3/UVI ACCUM UVIS-CEN F814W 3 none none none 1 775.0 S S TER 18126( 2) - 05-Aug-2025 16:01:14 - [ 10] Visit: 06 Visit Requirements: ORIENT 8D TO 38 D; ORIENT 98D TO 128 D; ORIENT 188D TO 218 D; ORIENT 278D TO 308 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-5 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=2 1 550 S PATTERN 3 1 0 S ER see below (2340 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PIE-FIELD-50 1 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 780.0 S S TER PIE-FIELD-50 1 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 1 780.0 S S TER PIE-FIELD-50 1 WFC3/UVI ACCUM UVIS-CEN F814W 3 none none none 1 780.0 S S TER 18126( 2) - 05-Aug-2025 16:01:14 - [ 11] Visit: 07 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-5 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=2 1 550 S PATTERN 3 1 2 S ER see below (2376 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PIE-FIELD-52 1 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 792.0 S S TER PIE-FIELD-52 1 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 1 792.0 S S TER PIE-FIELD-52 1 WFC3/UVI ACCUM UVIS-CEN F814W 3 none none none 1 792.0 S S TER 18126( 2) - 05-Aug-2025 16:01:14 - [ 12] Visit: 08 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PIE-FIELD-5 WFC3/UVI ACCUM UVIS-CENT F625W 1 550 S PATTERN 3 1 4 S ER see below (2382 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PIE-FIELD-54 1 WFC3/UVI ACCUM UVIS-CEN F625W 1 none none none 1 794.0 S S TER PIE-FIELD-54 1 WFC3/UVI ACCUM UVIS-CEN F625W 2 none none none 1 794.0 S S TER PIE-FIELD-54 1 WFC3/UVI ACCUM UVIS-CEN F625W 3 none none none 1 794.0 S S TER 18126( 2) - 05-Aug-2025 16:01:14 - [ 13] Summary Form for Proposal 18126 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=2 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 0D TO 30 D, ORIENT 101D TO 131 D, ORIENT 11D TO 41 D, ORIENT 158D TO 188 D, ORIENT 163D TO 193 D, ORIENT 180D TO 210 D, ORIENT 181D TO 211 D, ORIENT 188D TO 218 D, ORIENT 191D TO 221 D, ORIENT 1D TO 31 D, ORIENT 248D TO 278 D, ORIENT 253D TO 283 D, ORIENT 270D TO 300 D, ORIENT 271D TO 301 D, ORIENT 278D TO 308 D, ORIENT 281D TO 311 D, ORIENT 338D TO 8 D, ORIENT 343D TO 13 D, ORIENT 68D TO 98 D, ORIENT 73D TO 103 D, ORIENT 8D TO 38 D, ORIENT 90D TO 120 D, ORIENT 91D TO 121 D, ORIENT 98D TO 128 D, PATTERN 3 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F625W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PIE-FIELD-10, PIE-FIELD-20, PIE-FIELD-24, PIE-FIELD-28, PIE-FIELD-30, PIE-FIELD-50, PIE-FIELD-52, PIE-FIELD-54 ------------------------------------------------------------------------------------------------------------------------------------