17498( 5) - 28-Jun-2024 18:21:29 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17498 Version: 5 Check-in Time: 28-Jun-2024 18:21:29 STScI Edit Number: 1 Title The Ultra-faint Dwarf Galaxy System of NGC300 -- A New Frontier and Analog to the Large Magellanic Cloud ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. David J. Sand University of Arizona Y CoI: Dr. Alex Drlica-Wagner Fermi National Accelerator Laboratory N (FNAL) CoI: Dr. David Martinez-Delgado Instituto de Astrofisica de Andalucia N (IAA) CoI: Mr. Giuseppe Donatiello Unione Astrofili Italiani - UAI N CoI: Dr. Jeffrey L Carlin NOIRLab - Vera C. Rubin Operations (AZ) N CoI: Dr. Michael Gordon Jones University of Arizona N CoI: Dr. Burcin Mutlu-Pakdil Dartmouth College N CoI: Dr. Denija Crnojevic University of Tampa N CoI: Dr. Ananthan Karunakaran University of Toronto N CoI: Dr. Kristine Spekkens Royal Military College of Canada N CoI: Dr. Paul Bennet Space Telescope Science Institute N CoI: Dr. Catherine Fielder University of Arizona N ------------------------------------------------------------------------------------ Abstract We request three orbits of HST/ACS imaging (F606W+F814W) of three new ultra-faint dwarf galaxy candidates around NGC300 (D=2 Mpc), a nearby analog to the Large Magellanic Cloud (LMC). The faint end of the galaxy luminosity function is a strong probe of dark matter physics and galaxy formation models, but can only be studied in the most constraining "ultra-faint" regime in the nearby universe. Of particular interest are the dwarf satellite properties of lower mass LMC-like galaxies because these systems will experience weaker tidal fields and ram pressure environments in comparison to those of the Local Group, possibly leading to dwarfs with different physical properties. A search for dwarf satellites around the isolated LMC-analog NGC300 has uncovered three strong ultra-faint dwarf galaxy candidates, ranging in luminosity between M_V=-5.8 to -7 mag (log(M_star)~4.5--5). Two out of three of these discoveries are observed near the viral radius of NGC300, potentially probing its ram pressure environment. These candidate dwarf galaxy satellites represent the faintest population ever found outside the Local Group. HST imaging will allow us to measure the distance, luminosity, structure and approximate star formation history/metallicity of these dwarf candidates, and place them in context with similar ultra-faint dwarf galaxies near the Milky Way and LMC that have been discovered in the last ~20 years. ------------------------------------------------------------------------------------ Observations Description ------------------------ The observations will be performed with ACS/WFC (primary) and WFC3/UVIS (parallel). We request imaging in the F606W and F814W filters (broad V and I) 17498( 5) - 28-Jun-2024 18:21:29 - [ 2] for both instruments in order to compute accurate color-magnitude diagram based distances for our targets while characterizing their stellar content (e.g. star formation histories and metallicities) and structural parameters. 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. Our main target dwarf galaxies will be placed in the center of a chip -- we will use the WFC1 aperture. For each band we will use a two point ditherline pattern to mitigate hot pixels, cosmic rays, etc. We will not try to cover the chip gap as each dwarf fits well on a single chip. This program is resilient to two-gyro mode. 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. ------------------------------------------------------------------------------------ 17498( 5) - 28-Jun-2024 18:21:29 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC300DW1 GALAXY, DWARF RA=01H08M31.0000S, J2000 V = 22 SPHEROIDAL DEC=-36D03'54.00" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC300DW2 GALAXY, DWARF RA=01H06M51.0000S, J2000 V = 22 SPHEROIDAL DEC=-35D04'39.00" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC300DW3 GALAXY, DWARF RA=00H57M52.0000S, J2000 V = 22 SPHEROIDAL DEC=-35D51'14.00" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 17498( 5) - 28-Jun-2024 18:21:29 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.364 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 47.23 Angle_Between_Sides Center_Pattern NO Pattern_Comments: Two point dither. No need to fill chip gap. ------------------------------------------------------------------------------------------------------------------------------------ 17498( 5) - 28-Jun-2024 18:21:29 - [ 5] Visit: 01 (NGC300Dw1) 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 NGC300DW1 ACS/WFC ACCUM WFC1 F606W 1 600 S PATTERN 1 1 see below (954 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC300DW1 ACS/WFC ACCUM WFC1 F814W 1 600 S PATTERN 1 2 see below (954 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC300DW1 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 477.0 S NGC300DW1 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 477.0 S NGC300DW1 2 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 477.0 S NGC300DW1 2 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 477.0 S 17498( 5) - 28-Jun-2024 18:21:29 - [ 6] Visit: 02 (NGC300Dw2) 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 NGC300DW2 ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1010 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W FLASH=1.0 1 350 S S see below (1120 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC300DW2 ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1026 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=6.0 1 360 S S see below (1214 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC300DW2 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 295.0 S NGC300DW2 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 715.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 375 S S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 745.0 S S NGC300DW2 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 687.0 S NGC300DW2 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 339.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 749.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 465.0 S S 17498( 5) - 28-Jun-2024 18:21:29 - [ 7] Visit: 03 (NGC300Dw3) Visit Requirements: On Hold Comments: Additional Comments: There is a bright star near the center of the dwarf. 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 NGC300DW3 ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1010 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W FLASH=1.0 1 350 S S see below (1120 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC300DW3 ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1026 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W FLASH=6.0 1 360 S S see below (1214 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC300DW3 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 295.0 S NGC300DW3 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 715.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 375 S S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 745.0 S S NGC300DW3 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 687.0 S NGC300DW3 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 339. S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 749.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 465.0 S S 17498( 5) - 28-Jun-2024 18:21:29 - [ 8] Summary Form for Proposal 17498 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=1.0, FLASH=6.0 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PAR 2 WITH 1, PAR 4 WITH 3, PATTERN 1 1, PATTERN 1 1-2, PATTERN 1 2, PATTERN 1 3-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, NGC300DW1, NGC300DW2, NGC300DW3 ------------------------------------------------------------------------------------------------------------------------------------