17729( 5) - 18-Jun-2025 13:46:27 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17729 Version: 5 Check-in Time: 18-Jun-2025 13:46:27 STScI Edit Number: 1 Title Decoding Reionization Era using UV and IR spectral features ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Nimisha Kumari Space Telescope Science Institute - ESA - Y JWST CoI: Dr. Claus Leitherer Space Telescope Science Institute N CoI: Dr. Renske Smit Liverpool John Moores University N CoI: Dr. Joris Witstok Cosmic Dawn Center, Niels Bohr Institute N ------------------------------------------------------------------------------------ Abstract JWST and ALMA are revolutionizing the study of reionization-era galaxies by providing spectra of galaxies in the ultraviolet+optical and far infrared (FIR), respectively. Hence, it is urgent and crucial to establish a local reference sample of high-redshift "analog" galaxies covering UV, optical, and FIR. The UV and FIR carbon spectral features are seen in both low and high redshift galaxies with extreme properties. We build this proposal upon a multiwavelength pilot study of a reionization-era analog galaxy, Pox 186, showing extreme FIR [OIII]88/[CII]158 and high equivalent width of CIII]1909; and request HST/COS medium resolution FUV and NUV spectroscopy for three dwarf galaxies with high [OIII]/[CII] (>2) line ratios and high equivalent widths of [OIII]5007+Hbeta (>200 Angstrom) - the properties commonly observed in high-redshift galaxies. The requested COS/UV spectroscopy of these three galaxies will thereby double a sample of three Herschel dwarf galaxies with existing multiwavelength data and will allow us to characterize the properties of the pristine interstellar medium, massive stars, and infer parameters such as escape fraction of Lyman continuum and production efficiency of ionizing photons in a sample of reionization era analogs. These data will hence present a complete multiwavelength local reference sample and templates for rest-frame UV, optical, and FIR spectroscopy of early galaxies accessible by JWST and ALMA, and is a unique opportunity to decode puzzles of the reionization era. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to obtain high-quality (S/N >10) HST/COS spectra of three dwarf galaxies, which are potential local analogs of high-z (6~7) galaxies. We aim to detect the important nebular and stellar features ubiquitous at high-z such as CIV1548, 1550, He II 1640, OIII]1661, 1666 and CIII]1907, 1909 by using G160M and G185M to cover the wavelength range of (~1434-1796 A and ~1720-2027 A, respectively. The medium resolution COS gratings, G160M and G185M have sufficient spectral resolution required to resolve the CIV, OIII] and CIII] doublets mentioned above and will also be beneficial to resolve any broadening of the CIII] line profile. The existing UV spectroscopy (IUE, FOS) suffers from various issues (low S/N, insufficient wavelength coverage) as described in the sample selection. We prefer COS to STIS because of its higher sensitivity and better spectral resolution required for detecting 17729( 5) - 18-Jun-2025 13:46:27 - [ 2] and resolving various emission features. Two of the three targets are extended, which might affect the overall flux calibrations. However, this will not be a problem for most of our analysis which would be based on normalized spectra. We used the COS/ETC online tool to estimate the exposure times for target acquisition and spectroscopic observations of the three galaxies as described below: All our targets have GALEX images available. We estimated GALEX/FUV magnitudes for all point sources while GALEX/FUV surface brightness in the case of the extended source and then used them for normalization of a flat continuum source while estimating exposure time for Target acquisition via PSA and a recommended S/N=20. We will use Mirror A as recommended for NGC4861 while Mirror B for the other two targets that are too bright to observe with Mirror A. For spectroscopic observations, we used previously acquired spectra (IUE, FOS and G140L given in Table 1) within the COS/ETC to achieve a S/N>10 in emission lines of interest, i.e. CIII]1909 for G185M and CIV or OIII] for G185M. For UM461, no spectrum is currently available, so we assumed a flat continuum and normalized by GALEX/FUV surface brightness for extended source. For estimating the number of orbits, we assumed a conservative HST orbital time of 54 minutes, which excludes overheads related to guide-star re-acquisition and FP-POS split. The above method resulted in 15 orbits for observing three targets, comprising 6 orbits with G160M and 9 orbits with G185M. All proposed targets are safe to observe with HST/COS as no warnings (local or global) of violations are reported by the ETC. We will split the COS/UV spectroscopic observations within four FP-POS, which will serve various purposes, including an improved S/N. The G160M and G185M have dispersions of 73.4 and 103 mA resolution elements, respectively. We will fit the narrow Milky Way (MW) absorption features to estimate the approximate spectral resolution and then use them to bin the reduced and extracted one-dimensional spectra for achieving higher S/N. Our sample consists of nearby galaxies, which means COS aperture will cover spatial scales ranging from stellar clusters in galaxies to sub kiloparsec consisting of several HII regions, which will allow us to also study the effect of spatial scales in our analysis. If OIII] 1667 overlaps with the MW's Al II 1670 line, we will predict the strength of OIII] 1666 using the intrinsic emission line ratio of OIII] 1660, 1666 doublet. In total, we request 15 HST/COS orbits to acquire FUV and NUV spectra covering several emission lines within three galaxies, which show IR and optical properties similar to the EoR galaxies. ------------------------------------------------------------------------------------ 17729( 5) - 18-Jun-2025 13:46:27 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-2366 GALAXY, STAR FORMING RA=07H28M42.6803S +/- 0.1", J2000 V = 11.39 REGION DEC=+69D11'21.98" +/- 0.1" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 2 UM461 GALAXY, STAR FORMING RA=11H51M33.3534S +/- 0.2", J2000 V = 17.717 +/- 0.060 REGION DEC=-02D22'21.89" +/- 0.2" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-4861 GALAXY, STAR FORMING RA=12H59M0.2300S +/- 0.2", J2000 V = 12.32 REGION DEC=+34D50'43.50" +/- 0.2" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 17729( 5) - 18-Jun-2025 13:46:27 - [ 4] Visit: 01 (NGC-2366) 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 NGC-2366 COS/NUV ACQ/IMA PSA MIRRORB 1 2 S (2 S) GE ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-2366 COS/FUV TIME-TA PSA G160M 1623 FP-POS=ALL, BUFFER-TIME=8668 1 695 S G see below (4294 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-2366 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1172, FP-POS=ALL, 1 600 S G FLASH=YES see below (5302 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-2366 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE NGC-2366 2 COS/FUV TIME-TA PSA G160M 1623 none none none 1 1 968.0 S G NGC-2366 2 COS/FUV TIME-TA PSA G160M 1623 none none none 2 1 967.0 S G NGC-2366 2 COS/FUV TIME-TA PSA G160M 1623 none none none 3 2 1179.0 S G NGC-2366 2 COS/FUV TIME-TA PSA G160M 1623 none none none 4 2 1180.0 S G NGC-2366 3 COS/NUV TIME-TA PSA G185M 1900 none none none 1 3 1318.0 S G NGC-2366 3 COS/NUV TIME-TA PSA G185M 1900 none none none 2 3 1318.0 S G NGC-2366 3 COS/NUV TIME-TA PSA G185M 1900 none none none 3 4 1333.0 S G NGC-2366 3 COS/NUV TIME-TA PSA G185M 1900 none none none 4 4 1333.0 S G 17729( 5) - 18-Jun-2025 13:46:27 - [ 5] Visit: 02 (UM461) 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 UM461 COS/NUV ACQ/IMA PSA MIRRORB 1 16 S (16 GS ACQ SCENARIO BASE1O3 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 UM461 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=7471, FP-POS=ALL 1 1129 S G see below (3944 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=1, 1 1129 S G FLASH=YES see below (788 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=2, 1 1129 S G FLASH=YES see below (788 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=3, 1 1129 S G FLASH=YES see below (788 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 | ------------------------------------------------------------------------------------------------------------------------------------ UM461 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE UM461 2 COS/FUV TIME-TA PSA G160M 1623 none none none 1 1 880.0 S G UM461 2 COS/FUV TIME-TA PSA G160M 1623 none none none 2 1 879.0 S G UM461 2 COS/FUV TIME-TA PSA G160M 1623 none none none 3 2 1093.0 S G UM461 2 COS/FUV TIME-TA PSA G160M 1623 none none none 4 2 1092.0 S G UM461 3 COS/NUV TIME-TA PSA G185M 1900 none none none none 3 788.0 S G UM461 4 COS/NUV TIME-TA PSA G185M 1900 none none none none 3 788.0 S G UM461 5 COS/NUV TIME-TA PSA G185M 1900 none none none none 3 788.0 S G 17729( 5) - 18-Jun-2025 13:46:27 - [ 6] Visit: 03 (UM461) 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 UM461 COS/NUV ACQ/IMA PSA MIRRORB 1 16 S (16 GS ACQ SCENARIO BASE1O3 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=ALL, 1 1129 S G FLASH=YES see below (9680 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 | ------------------------------------------------------------------------------------------------------------------------------------ UM461 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE UM461 2 COS/NUV TIME-TA PSA G185M 1900 none none none 1 1 2162.0 S G UM461 2 COS/NUV TIME-TA PSA G185M 1900 none none none 2 2 2506 S G UM461 2 COS/NUV TIME-TA PSA G185M 1900 none none none 3 3 2506 S G UM461 2 COS/NUV TIME-TA PSA G185M 1900 none none none 4 4 2506.0 S G 17729( 5) - 18-Jun-2025 13:46:27 - [ 7] Visit: 04 (NGC-4861) 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 NGC-4861 COS/NUV ACQ/IMA PSA MIRRORB 1 3.5 S (3.5 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-4861 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=3796, FP-POS=ALL 1 374 S G see below (4038 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-4861 COS/NUV TIME-TA PSA G185M 1921 BUFFER-TIME=1140, FLASH=YES, 1 900 S G FP-POS=ALL see below (4992 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-4861 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE NGC-4861 2 COS/FUV TIME-TA PSA G160M 1623 none none none 1 1 903.0 S G NGC-4861 2 COS/FUV TIME-TA PSA G160M 1623 none none none 2 1 902.0 S G NGC-4861 2 COS/FUV TIME-TA PSA G160M 1623 none none none 3 2 1116.0 S G NGC-4861 2 COS/FUV TIME-TA PSA G160M 1623 none none none 4 2 1117.0 S G NGC-4861 3 COS/NUV TIME-TA PSA G185M 1921 none none none 1 3 1222.0 S G NGC-4861 3 COS/NUV TIME-TA PSA G185M 1921 none none none 2 3 1221.0 S G NGC-4861 3 COS/NUV TIME-TA PSA G185M 1921 none none none 3 4 1274.0 S G NGC-4861 3 COS/NUV TIME-TA PSA G185M 1921 none none none 4 4 1275.0 S G 17729( 5) - 18-Jun-2025 13:46:27 - [ 8] Visit: 13 (UM461) 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 UM461 COS/NUV ACQ/IMA PSA MIRRORB 1 16 S (16 GS ACQ SCENARIO BASE1O3 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=1, 1 1129 S G FLASH=YES see below (674 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=2, 1 1129 S G FLASH=YES see below (674 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=3, 1 1129 S G FLASH=YES see below (674 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=1, 1 1129 S G FLASH=YES see below (2598 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=2, 1 1129 S G FLASH=YES see below (2598 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 UM461 COS/NUV TIME-TA PSA G185M 1900 BUFFER-TIME=1183, FP-POS=3, 1 1129 S G FLASH=YES see below (2598 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 | ------------------------------------------------------------------------------------------------------------------------------------ UM461 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE UM461 2 COS/NUV TIME-TA PSA G185M 1900 none none none none 1 674.0 S G UM461 3 COS/NUV TIME-TA PSA G185M 1900 none none none none 1 674.0 S G UM461 4 COS/NUV TIME-TA PSA G185M 1900 none none none none 1 674.0 S G 17729( 5) - 18-Jun-2025 13:46:27 - [ 9] 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 | ------------------------------------------------------------------------------------------------------------------------------------ UM461 5 COS/NUV TIME-TA PSA G185M 1900 none none none none 2 2598.0 S G UM461 6 COS/NUV TIME-TA PSA G185M 1900 none none none none 3 2598.0 S G UM461 7 COS/NUV TIME-TA PSA G185M 1900 none none none none 4 2598.0 S G 17729( 5) - 18-Jun-2025 13:46:27 - [ 10] Summary Form for Proposal 17729 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1140, BUFFER-TIME=1172, BUFFER-TIME=1183, BUFFER-TIME=3796, BUFFER-TIME=7471, BUFFER-TIME=8668, FLASH=YES, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=ALL ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO BASE1O3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G160M, G185M, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC-2366, NGC-4861, UM461 ------------------------------------------------------------------------------------------------------------------------------------