17164( 3) - 05-Aug-2022 14:11:35 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17164 Version: 3 Check-in Time: 05-Aug-2022 14:11:35 STScI Edit Number: 0 Title Exploring The Plane of Satellites Around NGC253: A Case Study for Isolated Environments ------------------------------------------------------------------------------------ Type Cycle GO 30 ------------------------------------------------------------------------------------ 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. Michael Gordon Jones University of Arizona N CoI: Dr. Paul Bennet Space Telescope Science Institute N CoI: Dr. Ananthan Karunakaran Instituto de Astrofisica de Andalucia N (IAA) CoI: Dr. Kristine Spekkens Royal Military College of Canada N ------------------------------------------------------------------------------------ Abstract The distribution of dwarf satellite galaxies is a strong test for models of galaxy formation and evolution, independent of the exact details of baryonic physics. The three observed planes of satellites known today (around the Milky Way, M31, and Centaurus A) constitute a main problem for the standard cosmological models, where satellite systems are expected to have a nearly isotropic distribution. As these three systems reside in rich galaxy groups, their specific local environment could be responsible for the observed satellite planes. Exploration of satellite planes in other galaxies, in different environments, is thus a critical first step in solving the 'plane of satellites' problem. A spatially flattened dwarf satellite system has recently been proposed around NGC253 (D=3.5 Mpc), a Milky Way-mass spiral galaxy in an isolated environment. However, four faint dwarf candidates still lack distance measurements, and prevent us to draw a final conclusion on the true nature of this alleged plane of satellites (based on ten confirmed dwarf satellites). We request four orbits of HST/ACS in F606W and F814W to image these four NGC253 dwarf candidates in order to confirm their nature, precisely measure their distances, and study the 3D structure of the NGC253 dwarf satellite system as a whole. The results from this modest request will constrain the proposed plane of satellite galaxies in NGC253, an essential test for cosmological models in isolated environments. ------------------------------------------------------------------------------------ Observations Description ------------------------ The observations are going to be performed with ACS/WFC (primary) and WFC3/UVIS (parallel). 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. Our goal is to obtain a minimum SNR of ~10 at ~1 mag below the TRGB in I band, assuming that 17164( 3) - 05-Aug-2022 14:11:35 - [ 2] the TRGB is found at M_I=~-4.0 and M_V=~-2.5, in order to derive precise distance measurements, structural properties and average metallicities. With the requested SNR, the photometric errors will be ~0.05 mag in magnitude and ~0.1 mag in color at the TRGB. We will obtain distance uncertainties as low as ~0.1 mag, corresponding to ~150 kpc at the distance of NGC253. Since the exact distances for our targets are unknown, the candidate NGC253 satellites are assumed to be at the distance of NGC253 (~3.5 Mpc). Given their low masses, these are expected to be metal-poor objects, thus having average colours of V-I~1.5. At this distance, the TRGB is found at a magnitude of I~24.2 and V~25.7. The exposures to obtain the required SNR at 1 mag below the TRGB for both bands are ~ 1000 sec in F606W and ~ 1000 sec in F814W (as computed with the latest version of the ACS ETC), which result in one orbit per target. Each exposure will be split in two with a dither pattern in order to subsequently remove detector defects and improve the PSF sampling. We have checked that the charge transfer efficiency losses of ACS do not significantly affect our observations (at most 10% loss of flux). This program is resilient to two-gyro mode, we believe. 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. ------------------------------------------------------------------------------------ 17164( 3) - 05-Aug-2022 14:11:35 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 DOIII GALAXY, DWARF RA=01H09M24.5500S +/- 2", J2000 V = 18.75 SPHEROIDAL DEC=-27D20'49.60" +/- 2" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 2 DOIV GALAXY, DWARF RA=00H47M2.9500S +/- 2", J2000 V = 19.99 SPHEROIDAL DEC=-21D40'51.60" +/- 2" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 3 SCULPTORSR GALAXY, DWARF RA=00H33M51.7920S +/- 2", J2000 V = 17.8 SPHEROIDAL DEC=-27D50'24.00" +/- 2" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 4 DW0036M2828 GALAXY, DWARF RA=00H36M30.4800S +/- 2", J2000 V = 19.8 SPHEROIDAL DEC=-28D28'12.00" +/- 2" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 17164( 3) - 05-Aug-2022 14:11:35 - [ 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. ------------------------------------------------------------------------------------------------------------------------------------ 17164( 3) - 05-Aug-2022 14:11:35 - [ 5] 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 DOIII ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1006 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 350 S S (1100 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 DOIII ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1027 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W 1 360 S S see below (1215 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 | ------------------------------------------------------------------------------------------------------------------------------------ DOIII 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 286.0 S DOIII 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 720.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 N/A S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 750.0 S S DOIII 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 685.0 S DOIII 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 342.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 747.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 468.0 S S 17164( 3) - 05-Aug-2022 14:11:35 - [ 6] 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 DOIV ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (999 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 350 S S (1100 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 DOIV 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 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 | ------------------------------------------------------------------------------------------------------------------------------------ DOIV 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 279.0 S DOIV 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 720.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 N/A S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 750.0 S S DOIV 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 684.0 S DOIV 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 342.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 746.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 468.0 S S 17164( 3) - 05-Aug-2022 14:11:35 - [ 7] Visit: 03 Visit Requirements: ORIENT 44D TO 341 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 SCULPTORSR ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1006 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 350 S S (1100 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SCULPTORSR ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1027 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W 1 360 S S see below (1215 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 | ------------------------------------------------------------------------------------------------------------------------------------ SCULPTORSR 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 286.0 S SCULPTORSR 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 720.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 N/A S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 750.0 S S SCULPTORSR 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 685.0 S SCULPTORSR 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 342.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 747.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 468.0 S S 17164( 3) - 05-Aug-2022 14:11:35 - [ 8] Visit: 04 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 DW0036M2828 ACS/WFC ACCUM WFC1 F606W 1 650 S PATTERN 1 1-2; PAR 2 see below WITH 1 (1006 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 350 S S (1100 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 DW0036M2828 ACS/WFC ACCUM WFC1 F814W 1 450 S PATTERN 1 3-4; PAR 4 see below WITH 3 (1027 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F814W 1 360 S S see below (1215 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 | ------------------------------------------------------------------------------------------------------------------------------------ DW0036M2828 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 286.0 S DW0036M2828 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 720.0 S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 N/A S ANY 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 750.0 S S DW0036M2828 3 ACS/WFC ACCUM WFC1 F814W 1 none none none 1 685.0 S DW0036M2828 3 ACS/WFC ACCUM WFC1 F814W 2 none none none 1 342.0 S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 747.0 S S ANY 4 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 468.0 S S 17164( 3) - 05-Aug-2022 14:11:35 - [ 9] Summary Form for Proposal 17164 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 44D TO 341 D, PAR 2 WITH 1, PAR 4 WITH 3, PATTERN 1 1-2, PATTERN 1 3-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, DOIII, DOIV, DW0036M2828, SCULPTORSR ------------------------------------------------------------------------------------------------------------------------------------