18014( 4) - 03-Sep-2025 15:01:06 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18014 Version: 4 Check-in Time: 03-Sep-2025 15:01:06 STScI Edit Number: 0 Title An Extraordinary Strongly-Lensed Ly-C Leaker at z=4.059 ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Michael D. Gladders University of Chicago Y CoI: Dr. T. Emil Rivera-Thorsen Stockholm University N CoI: Prof. Keren Sharon University of Michigan N CoI: Dr. Haakon Dahle University of Oslo N CoI: Dr. Jane R. Rigby NASA Goddard Space Flight Center N CoI: Dr. Matthew Bayliss University of Cincinnati Main Campus N CoI: Dr. Brian Welch University of Maryland N CoI: Dr. Keunho J. Kim California Institute of Technology N CoI: Dr. Michael Florian University of Arizona N CoI: Dr. Taylor Alexandra Hutchison NASA Goddard Space Flight Center N CoI: Dr. Gourav Khullar University of Washington N CoI: Erik Solhaug University of Chicago N CoI: M. Riley Owens University of Cincinnati Main Campus N CoI: Ms. Sarah Grannis University of Chicago N CoI: Emory Murff University of Chicago N CoI: Camila Silva University of Chicago N CoI: Mr. Daniel Babnigg University of Chicago N CoI: Mr. Zewei Wu University of Chicago N CoI: Mr. Joseph Yeung University of Chicago N ------------------------------------------------------------------------------------ Abstract We propose HST imaging observations to measure the ionizing photons leaking from a remarkable z=4.059 strongly lensed galaxy. This galaxy, the highest redshift system yet identified to be spewing ionizing photons into the broader cosmos, and only the third strongly-lensed instance of a Ly-C leaker ever found, offers an opportunity to isolate and study the region(s) within the galaxy that are producing ionizing photons that are escaping. In addition to the direct measurement of the leaking ionizing photons we will also gather multi-band imaging, with both HST and JWST, to measure the continuum spectral energy distribitions of all structures within the galaxy. We also propose for initial exploratory JWST spectroscopy to measure restframes emission lines in the nebular gas. All of this imaging and spectroscopy will inform an analysis of the physical conditions within and properties of the leaking components, which be correlated with the leaking Ly-C photons known to be emerging from this galaxy. ------------------------------------------------------------------------------------ Observations Description ------------------------ This program is for imaging of a high redshift (z=4.06) strongly-lensed Lyman continuum leaker. The imaging from HST will be used for several purposes - including measuring the spatial distribution of the leaking photons and constructing a high fidelity lens model - and consist of imaging in 4 filters. 18014( 4) - 03-Sep-2025 15:01:06 - [ 2] Of the allocated 13 orbits, 7 will be used for imaging in the F438W filter; I have programed this as 2 2-orbit visits and 1 3-orbit visit. These data sample the Ly-C photons. To avoid post-flash losses in SNR, we take full orbit length images in each visit, dithered along a line; we add a small position offset to make sure the field is differently sampled (slightly) even if the visits end up occuring sequentially all at the sample rotation. We realise these offsets by specifying two slightly offset targets at +-2 arcsec. Because the lensing radius is reasonably small (maximally a few tens or arcseconds for all possible secondary image configurations) the whole system and all possible secondary lensd images fit comfortably on a single chip of WFC3, and we place the target accordingly on UVIS1-FIX; this places the target such that it will be well way from chip edges at all possible rotations. There are then 2 orbits each allocated to F547M, F606W and F814W, each programmed as a single 2-orbit visit. For each 2-orbit single filter observation, we observe a 4-point dither using a default WFC3-DITHER-UVIS-BOX pattern across the two orbits, to reject cosmic rays and bad pixels and sample the PSF for drizzling. The F547M images require a very slight postflash (level 2) to ensure that charge traps are well filled. ------------------------------------------------------------------------------------ 18014( 4) - 03-Sep-2025 15:01:06 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 COOLJ1402-28 GALAXY, GRAVITATIONAL RA=14H02M23.6160S, J2000 V = 22.3 09 LENS, HIGH REDSHIFT DEC=-28D09'37.44" GALAXY, PROTOGALAXY Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 2 COOLJ1402-28 GALAXY, GRAVITATIONAL RA=14H02M23.6160S, J2000 V = 22.3 09-OFFSETA LENS, HIGH REDSHIFT DEC=-28D09'35.44" GALAXY, PROTOGALAXY Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 3 COOLJ1402-28 GALAXY, GRAVITATIONAL RA=14H02M23.6160S, J2000 V = 22.3 09-OFFSETB LENS, HIGH REDSHIFT DEC=-28D09'39.44" GALAXY, PROTOGALAXY Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 18014( 4) - 03-Sep-2025 15:01:06 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18014( 4) - 03-Sep-2025 15:01:06 - [ 5] Visit: 01 (F547M) 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 COOLJ1402-2 WFC3/UVI ACCUM UVIS1-FIX F547M FLASH=2 1 1200 S PATTERN 1 1 809 S (4800 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 | ------------------------------------------------------------------------------------------------------------------------------------ COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F547M 1 none none none 1 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F547M 2 none none none 1 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F547M 3 none none none 2 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F547M 4 none none none 2 N/A S X 18014( 4) - 03-Sep-2025 15:01:06 - [ 6] Visit: 02 (F606W) 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 COOLJ1402-2 WFC3/UVI ACCUM UVIS1-FIX F606W 1 1200 S PATTERN 1 1 809 S (4800 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 | ------------------------------------------------------------------------------------------------------------------------------------ COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F606W 1 none none none 1 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F606W 2 none none none 1 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F606W 3 none none none 2 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F606W 4 none none none 2 N/A S X 18014( 4) - 03-Sep-2025 15:01:06 - [ 7] Visit: 03 (F814W) 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 COOLJ1402-2 WFC3/UVI ACCUM UVIS1-FIX F814W 1 1200 S PATTERN 1 1 809 S (4800 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 | ------------------------------------------------------------------------------------------------------------------------------------ COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F814W 1 none none none 1 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F814W 2 none none none 1 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F814W 3 none none none 2 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F814W 4 none none none 2 N/A S X 18014( 4) - 03-Sep-2025 15:01:06 - [ 8] Visit: 04 (F438W - 2pointA) 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 COOLJ1402-2 WFC3/UVI ACCUM UVIS1-FIX F438W 1 2530 S PATTERN 2 1 809-OFFSETA S (5060 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 | ------------------------------------------------------------------------------------------------------------------------------------ COOLJ1402-2809-OFFS 1 WFC3/UVI ACCUM UVIS1-FI F438W 1 none none none 1 N/A ETA S X COOLJ1402-2809-OFFS 1 WFC3/UVI ACCUM UVIS1-FI F438W 2 none none none 2 N/A ETA S X 18014( 4) - 03-Sep-2025 15:01:06 - [ 9] Visit: 05 (F438W - 2pointB) 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 COOLJ1402-2 WFC3/UVI ACCUM UVIS1-FIX F438W 1 2530 S PATTERN 2 1 809-OFFSETB S (5060 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 | ------------------------------------------------------------------------------------------------------------------------------------ COOLJ1402-2809-OFFS 1 WFC3/UVI ACCUM UVIS1-FI F438W 1 none none none 1 N/A ETB S X COOLJ1402-2809-OFFS 1 WFC3/UVI ACCUM UVIS1-FI F438W 2 none none none 2 N/A ETB S X 18014( 4) - 03-Sep-2025 15:01:06 - [ 10] Visit: 06 (F438W - 3point) 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 COOLJ1402-2 WFC3/UVI ACCUM UVIS1-FIX F438W 1 2530 S PATTERN 3 1 809 S (7590 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 | ------------------------------------------------------------------------------------------------------------------------------------ COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F438W 1 none none none 1 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F438W 2 none none none 2 N/A S X COOLJ1402-2809 1 WFC3/UVI ACCUM UVIS1-FI F438W 3 none none none 3 N/A S X 18014( 4) - 03-Sep-2025 15:01:06 - [ 11] Summary Form for Proposal 18014 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=2 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, PATTERN 2 1, PATTERN 3 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F438W, F547M, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names COOLJ1402-2809, COOLJ1402-2809-OFFSETA, COOLJ1402-2809-OFFSETB ------------------------------------------------------------------------------------------------------------------------------------