17514( 7) - 17-Jun-2024 16:13:01 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17514 Version: 7 Check-in Time: 17-Jun-2024 16:13:01 STScI Edit Number: 1 Title Three new isolated, faint and star-forming dwarf galaxies beyond the Local Group ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Burcin Mutlu-Pakdil Dartmouth College Y CoI: Prof. David J. Sand University of Arizona N CoI: Dr. Denija Crnojevic University of Tampa N CoI: Dr. Alex Drlica-Wagner Fermi National Accelerator Laboratory N (FNAL) CoI: Dr. Ananthan Karunakaran University of Toronto N CoI: Dr. Michael Gordon Jones University of Arizona N CoI: Dr. Kristine Spekkens Royal Military College of Canada N CoI: Dr. Catherine Fielder University of Arizona N CoI: Dr. Paul Bennet Space Telescope Science Institute N CoI: Kai Robert Herron Dartmouth College N CoI: Prof. Dennis Zaritsky University of Arizona N CoI: Richard Donnerstein University of Arizona N ------------------------------------------------------------------------------------ Abstract The Local Group satellite dwarf galaxies are frequently used as benchmarks for testing galaxy formation and evolution theories on the smallest scales because they are the lowest-mass galaxies for which we have detailed observations. However, the vast majority of these dwarfs have been affected by the Local Group environment. If we want to understand the physical mechanisms driving the evolution of low-mass galaxies, it is essential to study pristine isolated dwarf galaxies beyond the Local Group as a control sample. Unfortunately, identifying such galaxies in the field is extremely challenging due to their extreme faintness. To date, Leo P is the only known isolated, star-forming galaxy that is independent of group dynamics in an extremely low-mass regime (<10^6 Msun) but close enough at 1.6 Mpc to be studied with resolved stars. With only one system, it is challenging to draw broad conclusions about low-mass star-forming galaxies evolving in isolation. We request three orbits of HST/ACS imaging (F606W+F814W) to follow up three new nearby isolated, faint, star-forming dwarf galaxies discovered in ground-based surveys. The galaxies are likely just beyond the edge of the Local Group, with apparent morphologies and colors strikingly similar to Leo P. HST imaging is essential to the determination of secure distances, measurement of basic physical properties, and measurement of star formation histories of these three newly discovered dwarfs. The requested observations will put these three galaxies into context with other dwarf galaxies in and beyond the Local Group, providing a rare opportunity to assess the impact of environment on low-mass systems. ------------------------------------------------------------------------------------ Observations Description ------------------------ The observations are going to be performed with ACS/WFC (primary) and WFC3/UVIS 17514( 7) - 17-Jun-2024 16:13:01 - [ 2] (parallel) to match previous observations of faint dwarfs beyond the Local Group (e.g. Weisz et al. 2014, Hargis et al. 2020, Danieli et al. 2017, Bennet et al. 2019, Crnojevic et al. 2019, Mutlu-Pakdil et al 2022). We request imaging in F606W and F814W filters (broad V and I) for both instruments, in order to compute accurate TRGB distances for our targets and characterize their stellar content, while optimizing the exposure times. The parallel pointings will allow us to observe a field region next to our targets. We will thus be able to estimate more precisely the number of background/foreground contaminants present in our ACS fields. Given the small size of each target (<1 arcmin), one pointing is sufficient to cover the entire spatial extent of each galaxy. Each dwarf will be placed on one of the ACS/WFC chips, and small dithers between exposures will remove detector defects and improve the PSF sampling. Given that the possible distance range for our targets is ~1-3 Mpc, we use existing HST ACS data of Local Volume dwarfs at <3 Mpc (NGC253 dwarfs [GO-14259, GO-15938], CenA dwarfs [GO-13856], MADCASH dwarfs [GO-15228]) to guide our observational request and ensure that the depth is sufficient for the science goals of this proposal. The archival ACS data for similar limiting magnitudes were obtained with 2 CR-SPLIT exposures of 1200 sec in F606W and 900 sec in F814W. The required exposure times nicely fit into one orbit per object after taking into account realistic overheads. With these exposures, the achieved SNR given by the ACS ETC is ~10 at 1 mag below the TRGB for both bands (assuming a distance of 3~Mpc), with a limiting magnitude of ~27 in F814W, thus fulfilling our requirements. This translates into only a total of three orbits for our three dwarfs. We have checked that the charge transfer efficiency losses of ACS do not significantly affect our observations (at most 10% loss of flux). Our visits are 1-orbit, and we have no ORIENT requirements. Nor does this program have time constraints (other than the baseline excitement of the science!). We can also achieve our science goals with a longer acquisition time, if necessary. ------------------------------------------------------------------------------------ 17514( 7) - 17-Jun-2024 16:13:01 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CORVUS GALAXY, DWARF RA=12H14M45.8400S, J2000 V = 16 +/- 0.1 SPHEROIDAL DEC=-16D23'49.92" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 2 KAMINO GALAXY, DWARF RA=04H15M49.1280S, J2000 V = 16 +/- 0.1 SPHEROIDAL DEC=-60D43'51.24" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 3 PAVO GALAXY, DWARF RA=19H55M0.4800S, J2000 V = 16 +/- 0.1 SPHEROIDAL DEC=-61D04'40.08" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 17514( 7) - 17-Jun-2024 16:13:01 - [ 4] Visit: 01 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 CORVUS ACS/WFC ACCUM WFC2 F606W 1 270 S (270 PAR 2 WITH 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W FLASH=5 1 345 S (345 S S) ------------------------------------------------------------------------------------------------------------------------------------ 3 CORVUS ACS/WFC ACCUM WFC2 F606W 1 710 S (710 POS TARG 0.25, 0.27; PAR S) 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F606W 1 720 S (720 S S) ------------------------------------------------------------------------------------------------------------------------------------ 5 CORVUS ACS/WFC ACCUM WFC2 F814W 1 685 S (685 PAR 6 WITH 5 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=6 1 737 S (737 S S) ------------------------------------------------------------------------------------------------------------------------------------ 7 CORVUS ACS/WFC ACCUM WFC2 F814W 1 342 S (342 POS TARG 0.25, 0.27; PAR S) 8 WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=6 1 468 S (468 S 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 | ------------------------------------------------------------------------------------------------------------------------------------ CORVUS 1 ACS/WFC ACCUM WFC2 F606W none none none none 1 N/A ANY 2 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S CORVUS 3 ACS/WFC ACCUM WFC2 F606W none none none none 1 N/A ANY 4 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S CORVUS 5 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A ANY 6 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S CORVUS 7 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A ANY 8 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S 17514( 7) - 17-Jun-2024 16:13:01 - [ 5] Visit: 02 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 KAMINO ACS/WFC ACCUM WFC2 F606W 1 400 S (400 PAR 2 WITH 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W FLASH=5 1 400 S (400 S S) ------------------------------------------------------------------------------------------------------------------------------------ 3 KAMINO ACS/WFC ACCUM WFC2 F606W 1 729 S (729 POS TARG 0.25, 0.27; PAR S) 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F606W 1 750 S (750 S S) ------------------------------------------------------------------------------------------------------------------------------------ 5 KAMINO ACS/WFC ACCUM WFC2 F814W 1 695 S (695 PAR 6 WITH 5 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=6 1 747 S (747 S S) ------------------------------------------------------------------------------------------------------------------------------------ 7 KAMINO ACS/WFC ACCUM WFC2 F814W 1 450 S (450 POS TARG 0.25, 0.27; PAR S) 8 WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=6 1 468 S (468 S 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 | ------------------------------------------------------------------------------------------------------------------------------------ KAMINO 1 ACS/WFC ACCUM WFC2 F606W none none none none 1 N/A ANY 2 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S KAMINO 3 ACS/WFC ACCUM WFC2 F606W none none none none 1 N/A ANY 4 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S KAMINO 5 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A ANY 6 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S KAMINO 7 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A ANY 8 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S 17514( 7) - 17-Jun-2024 16:13:01 - [ 6] Visit: 03 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 PAVO ACS/WFC ACCUM WFC2 F606W 1 286 S (286 PAR 2 WITH 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W FLASH=5 1 360 S (360 S S) ------------------------------------------------------------------------------------------------------------------------------------ 3 PAVO ACS/WFC ACCUM WFC2 F606W 1 720 S (720 POS TARG 0.25, 0.27; PAR S) 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F606W 1 750 S (750 S S) ------------------------------------------------------------------------------------------------------------------------------------ 5 PAVO ACS/WFC ACCUM WFC2 F814W 1 926 S (926 PAR 6 WITH 5 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=6 1 747 S (747 S S) ------------------------------------------------------------------------------------------------------------------------------------ 7 PAVO ACS/WFC ACCUM WFC2 F814W 1 342 S (342 POS TARG 0.25, 0.27; PAR S) 8 WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=6 1 468 S (468 S 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 | ------------------------------------------------------------------------------------------------------------------------------------ PAVO 1 ACS/WFC ACCUM WFC2 F606W none none none none 1 N/A ANY 2 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S PAVO 3 ACS/WFC ACCUM WFC2 F606W none none none none 1 N/A ANY 4 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S PAVO 5 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A ANY 6 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S PAVO 7 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A ANY 8 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S 17514( 7) - 17-Jun-2024 16:13:01 - [ 7] Visit: 52 Visit Requirements: On Hold Comments: Additional Comments: Repeat of visit 02 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 KAMINO ACS/WFC ACCUM WFC2 F606W 1 400 S (400 PAR WITH 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 KAMINO ACS/WFC ACCUM WFC2 F606W 1 595 S (595 POS TARG 0.25, 0.27; PAR S) WITH 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 KAMINO ACS/WFC ACCUM WFC2 F814W 1 595 S (595 PAR WITH 3 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 KAMINO ACS/WFC ACCUM WFC2 F814W 1 400 S (400 POS TARG 0.25, 0.27; PAR S) WITH 4 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ KAMINO 1 ACS/WFC ACCUM WFC2 F606W none none none none 1 N/A KAMINO 2 ACS/WFC ACCUM WFC2 F606W none none none none 1 N/A KAMINO 3 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A KAMINO 4 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A 17514( 7) - 17-Jun-2024 16:13:01 - [ 8] Summary Form for Proposal 17514 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, WFC2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=5, FLASH=6 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PAR WITH 1, PAR WITH 2, PAR WITH 3, PAR WITH 4, PAR 2 WITH 1, PAR 4 WITH 3, PAR 6 WITH 5, PAR 8 WITH 7, POS TARG 0.25, 0.27 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, CORVUS, KAMINO, PAVO ------------------------------------------------------------------------------------------------------------------------------------