18074( 4) - 27-Jan-2026 02:40:33 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18074 Version: 4 Check-in Time: 27-Jan-2026 02:40:33 STScI Edit Number: 0 Title PANCHO: Piloting a Novel Calibration for H2 Observations ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Ava Polzin University of Chicago Y CoI: Prof. Hsiao-Wen Chen University of Chicago Y CoI: Dr. Zhijie Qu Tsinghua University Y CoI: Dr. Andrey V. Kravtsov University of Chicago N CoI: Prof. Nickolay Gnedin Fermi National Accelerator Laboratory N (FNAL) CoI: Dr. Vadim Semenov Harvard University N ------------------------------------------------------------------------------------ Abstract Very low metallicity galaxies are a frontier in modern astrophysics. Locally, they represent the exreme low mass end of galaxy formation. At early cosmic time, when the global metallicity is lower, they are the result of some of the earliest galaxy formation in the universe. Despite their importance on a range of scales, understanding the formation and evolution of such galaxies - including the connection between their chemical and physical properties - is a significant challenge due to their generally low masses and/or high redshifts. There is a disparity between observed star formation in low metallicity galaxies and the most common models of star formation inferred from more numerous observations of higher metallicity, often higher mass, galaxies. As a result, the mechanism and medium for star formation in less metal-enriched galaxies is uncertain. A primary constraint can be placed on the nature of star formation using directly measured molecular hydrogen abundance. To date, this has been a challenge since absorption spectroscopy, by necessity, covers only a limited angular extent toward a sometimes ionizing background source. This pilot program capitalizes on the molecular and atomic lines in the HST COS FUV bands to, in conjunction with archival 21 cm emission maps, obtain spatially resolved molecular hydrogen content along two sightines in IC1613. IC1613 is one of best-studied low metallicity galaxies, providing a unique testbed for star formation models. These observations will: (1) extend UV absorption constraints of H2 to external galaxies and (2) place initial constraints on the nature and regulation of star formation in low metallicity galaxies. ------------------------------------------------------------------------------------ Observations Description ------------------------ This is a pilot program to use HST COS to obtain spatially resolved molecular hydrogen measurements in absorption along two individual sightlines toward FUV-bright stars. The approved observing program involves two individual spectroscopic pointings, one for each star, with G130M (and central wavelength of 1096AA). A total of 26 orbits are approved with 11 orbits on one target and 15 orbits for the second to ensure consistent signal-to-noise ratios for both targets. 18074( 4) - 27-Jan-2026 02:40:33 - [ 2] Both targets are in a nearby galaxy, and IC1613-A13 is in a less dense environment, while IC1613-B3 is in a more crowded environment that necessitates careful acquisition. ------------------------------------------------------------------------------------ 18074( 4) - 27-Jan-2026 02:40:33 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 IC1613-A13 STAR, MAIN SEQUENCE O RA=01H05M6.2560S +/- 0.2", J2000 V = 19.02 DEC=+02D10'43.15" +/- 0.2" Reference Frame: ICRS Extended: NO Comments: Coordinates from HST GO-12587 ------------------------------------------------------------------------------------------------------------------------------------ 1 IC1613-B3 STAR, B0-B2 III-I RA=01H05M6.3767S +/- 0.2", J2000 V = 17.81 DEC=+02D09'31.39" +/- 0.2" Reference Frame: ICRS Extended: NO Comments: Coordinates from WFC3 F275W image. ------------------------------------------------------------------------------------------------------------------------------------ 18074( 4) - 27-Jan-2026 02:40:33 - [ 4] Visit: 01 (IC1613-B3) 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 IC1613-B3 COS/NUV ACQ/IMA PSA MIRRORB 1 15 S (15 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=1, BUFFER-TIME=380 1 2029 S G (2029 S) Comments: The ETC is for the full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 3 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=2, BUFFER-TIME=380 1 2539 S G (2539 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=3, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 5 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=4, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC1613-B3 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE IC1613-B3 2 COS/FUV TIME-TA PSA G130M 1096 none none none none 1 N/A G IC1613-B3 3 COS/FUV TIME-TA PSA G130M 1096 none none none none 2 N/A G IC1613-B3 4 COS/FUV TIME-TA PSA G130M 1096 none none none none 3 N/A G IC1613-B3 5 COS/FUV TIME-TA PSA G130M 1096 none none none none 4 N/A G 18074( 4) - 27-Jan-2026 02:40:33 - [ 5] Visit: 02 (IC1613-B3) 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 IC1613-B3 COS/NUV ACQ/IMA PSA MIRRORB 1 15 S (15 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=1, BUFFER-TIME=380 1 2029 S G (2029 S) Comments: ETC is for full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 3 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=2, BUFFER-TIME=380 1 2539 S G (2539 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=3, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 5 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=4, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC1613-B3 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE IC1613-B3 2 COS/FUV TIME-TA PSA G130M 1096 none none none none 1 N/A G IC1613-B3 3 COS/FUV TIME-TA PSA G130M 1096 none none none none 2 N/A G IC1613-B3 4 COS/FUV TIME-TA PSA G130M 1096 none none none none 3 N/A G IC1613-B3 5 COS/FUV TIME-TA PSA G130M 1096 none none none none 4 N/A G 18074( 4) - 27-Jan-2026 02:40:33 - [ 6] Visit: 03 (IC1613-B3) 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 IC1613-B3 COS/NUV ACQ/IMA PSA MIRRORB 1 15 S (15 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=1, BUFFER-TIME=380 1 2029 S G (2029 S) Comments: ETC is for full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 3 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=3, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 4 IC1613-B3 COS/FUV TIME-TA PSA G130M 1096 FP-POS=4, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (11 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC1613-B3 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE IC1613-B3 2 COS/FUV TIME-TA PSA G130M 1096 none none none none 1 N/A G IC1613-B3 3 COS/FUV TIME-TA PSA G130M 1096 none none none none 2 N/A G IC1613-B3 4 COS/FUV TIME-TA PSA G130M 1096 none none none none 3 N/A G 18074( 4) - 27-Jan-2026 02:40:33 - [ 7] Visit: 05 (IC16113-A13) 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 IC1613-A13 COS/NUV ACQ/IMA PSA MIRRORA 1 6.5 S (6.5 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=1, BUFFER-TIME=380 1 2047 S G (2047 S) Comments: ETC for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 3 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=2, BUFFER-TIME=380 1 2539 S G (2539 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=3, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 5 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=4, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC1613-A13 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE IC1613-A13 2 COS/FUV TIME-TA PSA G130M 1096 none none none none 1 N/A G IC1613-A13 3 COS/FUV TIME-TA PSA G130M 1096 none none none none 2 N/A G IC1613-A13 4 COS/FUV TIME-TA PSA G130M 1096 none none none none 3 N/A G IC1613-A13 5 COS/FUV TIME-TA PSA G130M 1096 none none none none 4 N/A G 18074( 4) - 27-Jan-2026 02:40:33 - [ 8] Visit: 06 (IC16113-A13) 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 IC1613-A13 COS/NUV ACQ/IMA PSA MIRRORA 1 6.5 S (6.5 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=1, BUFFER-TIME=380 1 2047 S G (2047 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 3 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=2, BUFFER-TIME=380 1 2539 S G (2539 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=3, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 5 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=4, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC1613-A13 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE IC1613-A13 2 COS/FUV TIME-TA PSA G130M 1096 none none none none 1 N/A G IC1613-A13 3 COS/FUV TIME-TA PSA G130M 1096 none none none none 2 N/A G IC1613-A13 4 COS/FUV TIME-TA PSA G130M 1096 none none none none 3 N/A G IC1613-A13 5 COS/FUV TIME-TA PSA G130M 1096 none none none none 4 N/A G 18074( 4) - 27-Jan-2026 02:40:33 - [ 9] Visit: 07 (IC16113-A13) 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 IC1613-A13 COS/NUV ACQ/IMA PSA MIRRORA 1 6.5 S (6.5 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=1, BUFFER-TIME=380 1 2047 S G (2047 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 3 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=2, BUFFER-TIME=380 1 2539 S G (2539 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=3, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 5 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=4, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC1613-A13 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE IC1613-A13 2 COS/FUV TIME-TA PSA G130M 1096 none none none none 1 N/A G IC1613-A13 3 COS/FUV TIME-TA PSA G130M 1096 none none none none 2 N/A G IC1613-A13 4 COS/FUV TIME-TA PSA G130M 1096 none none none none 3 N/A G IC1613-A13 5 COS/FUV TIME-TA PSA G130M 1096 none none none none 4 N/A G 18074( 4) - 27-Jan-2026 02:40:33 - [ 10] Visit: 08 (IC16113-A13) 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 IC1613-A13 COS/NUV ACQ/IMA PSA MIRRORA 1 6.5 S (6.5 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=1, BUFFER-TIME=380 1 2047 S G (2047 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 3 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=3, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 4 IC1613-A13 COS/FUV TIME-TA PSA G130M 1096 FP-POS=4, BUFFER-TIME=380 1 2539 S G (2539 S) Comments: ETC is for full integration (15 orbits). ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC1613-A13 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE IC1613-A13 2 COS/FUV TIME-TA PSA G130M 1096 none none none none 1 N/A G IC1613-A13 3 COS/FUV TIME-TA PSA G130M 1096 none none none none 2 N/A G IC1613-A13 4 COS/FUV TIME-TA PSA G130M 1096 none none none none 3 N/A G 18074( 4) - 27-Jan-2026 02:40:33 - [ 11] Summary Form for Proposal 18074 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=380, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORA, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names IC1613-A13, IC1613-B3 ------------------------------------------------------------------------------------------------------------------------------------