17714( 3) - 24-Apr-2025 18:12:36 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17714 Version: 3 Check-in Time: 24-Apr-2025 18:12:36 STScI Edit Number: 0 Title Understanding the Role of Massive Stars in Galaxies at Cosmic Noon in a Legacy Spectroscopic Field ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Tim Blake Miller Northwestern University Y CoI: Prof. Allison L. Strom Northwestern University N CoI: Prof. Ryan F Trainor Franklin and Marshall College N CoI: Dr. Gwen C. Rudie Carnegie Institution of Washington N CoI: Dr. Noah Sidney James Rogers Northwestern University N CoI: Caroline von Raesfeld Northwestern University N CoI: Dr. Guochao Sun Northwestern University N ------------------------------------------------------------------------------------ Abstract We propose to use new HST/ACS imaging in F606W and F814W to create high spatial resolution rest-UV maps for z~2 star-forming galaxies in the field surrounding luminous quasar Q2343+125. This field stands out in terms of spectroscopic investment, with deep (~10 hr) rest-UV spectra from Keck/LRIS, deep (~2-10 hr) rest-optical spectra from Keck/MOSFIRE, and ultra-deep (~30 hr) rest-optical and rest-NIR spectra from JWST/NIRSpec. This unique combination enables a detailed accounting of the ionizing spectra of massive stars using direct observations of their rest-UV continua and myriad HII emission lines spanning rest-frame ~0.3-1.1 micron. The proposed imaging will allow us to study the rest-UV morphology of these galaxies for the first time, thereby addressing two outstanding questions related to the distribution of massive stars in high-z galaxies: First, we will investigate the connection between ionization conditions and galaxy morphology. This study will serve as a bridge to understanding this connection at even higher redshifts, where knowledge of how the clustering of massive stars affects galaxies' ionizing output is urgently needed to determine their contribution to cosmic reionization. Second, we will use these data to provide improved guidance to the community about how best to combine space- and ground-based spectroscopy, which are often observed at very different spatial scales. A comparatively small investment of HST time will significantly enhance the legacy value of one of richest spectroscopic datasets of distant galaxies ever assembled and provide novel constraints on the properties of massive stars--and their impact on galaxies--at Cosmic Noon and beyond. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to obtain rest-UV imaging in two filters (F606W and F814W) over the footprint of the CECILIA JWST NIRSpec/MSA observations. The principal scientific goals of these observations are to perform resolved SED fitting and determine the rest-UV morphologies of z = 2 galaxies (Sec. 2) and improve slit-loss corrections (Sec. 3). We choose the F606W 17714( 3) - 24-Apr-2025 18:12:36 - [ 2] and F814W filters as they sample the rest-UV continuum from rest wavelength = 1500- 3000 angstrom of the targeted galaxies at z = 2 (see Fig. 1). We require two bands, in addition to the rest- optical F140W observations obtained as part of HST C24 GO 14620, in order to perform resolved SED fitting and study the relationship between ionization conditions and the distribution of star formation with a galaxy. Multiple bands are needed to successfully break the degeneracy between dust attenuation and star formation in the rest-UV (e.g., Miller et al., 2022). The parent galaxy sample has a median RAB = 24.58, with an interquartile range of R band mage = 24.12 - 25.01 at a median z = 2.4. The median semi-major (half-light) axis is 0.26 arcsec, with an axis ratio of b/a = 0.6. In order to perform resolved SED fitting and calculate accurate slit-loss corrections, we require a S/N per pixel of > 5 out to the effective radius. This corresponds to an integrated S/N > 20, above the suggested benchmark of S/N = 15 for traditional morphological analysis (e.g., Shibuya et al., 2015). Using the median properties of our sample and the HST/ACS ETC, we find that achieving this S/N requires 13 ks and 22 ks in the F606W and F814W filters, respectively. The orbital visibility of our target field is 52 min, so we request a total of 11 orbits: 4 in F606W and 7 in F814W ------------------------------------------------------------------------------------ 17714( 3) - 24-Apr-2025 18:12:36 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 Q2343+125 GALAXY, QUASAR RA=23H46M27.2890S, J2000 V = 17.5 DEC=+12D48'7.50" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 17714( 3) - 24-Apr-2025 18:12:36 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE ACS-WFC-DITHER-LINE Pattern_Purpose DITHER DITHER Number_Of_Points 2 2 Point_Spacing 3.034 0.149 Line_Spacing Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 85.29 34.25 Angle_Between_Sides Center_Pattern NO NO ------------------------------------------------------------------------------------------------------------------------------------ 17714( 3) - 24-Apr-2025 18:12:36 - [ 5] Visit: 01 (F606w - 2 orb - 1) Visit Requirements: ORIENT 198.5D TO 213.5 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 Q2343+125 ACS/WFC ACCUM WFC F606W 2 548 S POS TARG see below -1.5426810976800902, (4020 S) -0.9470887873046967; PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ Q2343+125 1 ACS/WFC ACCUM WFC F606W 1 1 1 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 1 1 2 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 1 2 1 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 1 2 2 none 1 496.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 2 1 1 none 2 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 2 1 2 none 2 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 2 2 1 none 2 553.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 2 2 2 none 2 496.0 S 17714( 3) - 24-Apr-2025 18:12:36 - [ 6] Visit: 02 (F606w - 2 orb - 2) Visit Requirements: ORIENT 198.5D TO 213.5 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 Q2343+125 ACS/WFC ACCUM WFC F606W 2 548 S POS TARG see below -1.5426810976800902, (4020 S) -0.9470887873046967; PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ Q2343+125 1 ACS/WFC ACCUM WFC F606W 1 1 1 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 1 1 2 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 1 2 1 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 1 2 2 none 1 496.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 2 1 1 none 2 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 2 1 2 none 2 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 2 2 1 none 2 553.0 S Q2343+125 1 ACS/WFC ACCUM WFC F606W 2 2 2 none 2 496.0 S 17714( 3) - 24-Apr-2025 18:12:36 - [ 7] Visit: 03 (F814w - 2 orb - 1) Visit Requirements: ORIENT 198.5D TO 213.5 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 Q2343+125 ACS/WFC ACCUM WFC F814W 2 548 S POS TARG see below -1.5426810976800902, (4020 S) -0.9470887873046967; PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 1 1 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 1 2 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 2 1 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 2 2 none 1 496.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 1 1 none 2 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 1 2 none 2 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 2 1 none 2 553.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 2 2 none 2 496.0 S 17714( 3) - 24-Apr-2025 18:12:36 - [ 8] Visit: 04 (F814w - 2 orb - 2) Visit Requirements: ORIENT 198.5D TO 213.5 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 Q2343+125 ACS/WFC ACCUM WFC F814W 2 548 S POS TARG see below -1.5426810976800902, (4020 S) -0.9470887873046967; PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 1 1 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 1 2 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 2 1 none 1 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 2 2 none 1 496.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 1 1 none 2 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 1 2 none 2 495.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 2 1 none 2 553.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 2 2 none 2 496.0 S 17714( 3) - 24-Apr-2025 18:12:36 - [ 9] Visit: 05 (F814w - 3 orb) Visit Requirements: ORIENT 198.5D TO 213.5 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 Q2343+125 ACS/WFC ACCUM WFC F814W 3 548 S POS TARG see below -1.5426810976800902, (6103 S) -0.9470887873046967; PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 1 1 none 1 481.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 1 2 none 1 500.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 1 3 none 1 500.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 2 1 none 1 500.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 2 2 none 2 518.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 1 2 3 none 2 500.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 1 1 none 2 541.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 1 2 none 2 500.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 1 3 none 3 541.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 2 1 none 3 522.0 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 2 2 none 3 500 S Q2343+125 1 ACS/WFC ACCUM WFC F814W 2 2 3 none 3 500 S 17714( 3) - 24-Apr-2025 18:12:36 - [ 10] Summary Form for Proposal 17714 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 198.5D TO 213.5 D, PATTERN 2 1, POS TARG -1.5426810976800902, -0.9470887873046967 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names Q2343+125 ------------------------------------------------------------------------------------------------------------------------------------