18020( 2) - 08-Aug-2025 17:17:37 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18020 Version: 2 Check-in Time: 08-Aug-2025 17:17:37 STScI Edit Number: 0 Title The Extended Clusters of Andromeda - dwarf galaxies or globular clusters? ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Michelle L.M. Collins University of Surrey Y CoI: Dr. Amandine Doliva-Dolinsky University of Surrey N CoI: Astha Astha University of Surrey N CoI: Ms. Izzy Gray University of Surrey N CoI: Mrs. Mahdieh Navabi University of Surrey N CoI: Susan Hutton University of Surrey N CoI: Dr. Noelia Noel University of Surrey N CoI: Connor Pickett University of Surrey N CoI: Prof. Justin Read University of Surrey N CoI: Dr. R. Michael Rich University of California - Los Angeles N CoI: Ms. Joanna Sakowska University of Surrey N CoI: Mr. Ethan Taylor University of Surrey N ------------------------------------------------------------------------------------ Abstract New survey data continues to blur the boundary between Globular Clusters (GCs), thought to be single stellar populations devoid of dark matter, and dwarf galaxies. The extended clusters (ECs) of Andromeda were first discovered in 2005 and sit right in the gap between these two populations. Given their sizes (half light radii of ~30pc) and brightnesses (Mv ~ -6), it was unclear whether these were puffed up globular star clusters, or faint dwarf galaxies. In the nearly two decades since, we are still unsure of their nature. Spectroscopic data have shown they could be either dark matter dominated or dark matter free, while shallow HST imaging to their horizontal branches have shown them to have stellar populations consistent with either population. One clear method to break this frustrating degeneracy is to measure their star formation histories. GCs form their stars essentially in a single burst, while even the faintest dSphs have star formation that extends over a Gyr or more. By measuring their star formation histories we can determine which class ECs belong to for the first time, offering a unique opportunity to refine our definition of GCs and dwarfs, test GC formation models and refine using galaxy counts of the faintest dwarfs as a cosmological probe. To achieve our goals, we request 33 orbits of WFC3 observations to image three bright ECs down to their oldest main sequence turn-offs. ------------------------------------------------------------------------------------ 18020( 2) - 08-Aug-2025 17:17:37 - [ 2] Observations Description ------------------------ We propose one field of WFC3 imaging for three ECs in M31. We have selected three bright ECs in Andromeda with reliable existing shallow HST data. Our strategy follows previous campaigns that measure SFHs from the oldest MSTO of faint objects in the Local Group. These include the ISLAndS (Skillman et al. 2017) and M31 dSph multi-cycle treasury programs (Savino et al. 2025). We select the F606W-F814W filter combination, and aim to reach a S/N = 10 at the oldest MSTO (MI = +3.0 for ages of 12.5 Gyr or F814W~27.4 for all our objects.). This is the benchmark required for high fidelity recovery of the SFH at ancient ages (e.g. Savino et al 2023, 2025). As we use the same filter set as for all other M31 dwarf galaxies, we can compare directly with the CMDs and SFHs for the full M31 satellite population (Skillman et al 2017; Savino et al. 2022, 2023). The ECs are compact (~30"), fitting easily within the field-of-view of WFC3. This leaves a significant area around the EC in the WFC3 field, allowing us to well-sample the foreground population and clean our observations of contaminants. Our proposed depth means we reliably distinguish between stellar and galaxy sources even at the oldest MSTO (Radburn-Smith 2011) as the photometric uncertainties do not dominate the observations. Ground based telescopes cannot reach the oldest MSTO stars in the M31 ECs. HST is therefore essential in unlocking the nature of Extended Clusters. While JWST would allow a determination of the SFHs, HST allows us to compare directly with the previous EC observations, and the full M31 satellite system. To reach our precision of S/N = 10 at the MSTO, we require exposure times of 9, 051 sec in F606W and 19, 640-sec in F814W for each EC. Including standard overheads, this results in 11 orbits per EC, giving a total request of 33 orbits. We will use 4-point dither patterns to achieve 0.5 pixel sampling. The data will be reduced and analyzed with standard well-tested methods. The DOLPHOT stellar photometry package will measure the point spread function photometry (e.g. Dolphin et al. 2000; Monelli et al. 2010) using a similar setup to the Panchromatic Hubble Andromeda Treasury survey (PHAT, Williams et al. 2014). We will perform 18020( 2) - 08-Aug-2025 17:17:37 - [ 3] artificial star tests on our final images to accurately determine photometric errors and incompleteness in each band. We exploit the excellent S/N at the oldest MSTO to compute detailed SFHs and measure the duration of star formation with a precision of < 500 Myr. The difference in the stellar populations at the MSTO will clearly be seen in our data, as shown in Fig. 2 where we show model CMDs for a GC and dSph with the brightness of our targets, as well as the difference between them in the Hess diagram. The SFHs will be derived using CMD fitting software MATCH, which has been previously used to obtain SFHs from comparably deep HST imaging for M31 dwarf galaxies (e.g. Savino et al. 2025). As stellar evolution models are the key systematic uncertainty in CMD modeling, we plan to run SFHs using at least two different stellar evolution models (PARSEC, Bressan et al. 2012 and BASTI, Pietrinferni et al. 2004, Hidalgo et al. 2018) and to obtain mock stellar models that include systematic shifts in the stellar evolutionary tracks, luminosities and temperatures. We will position our ECs in the center of one of the two WFC3 chips. Once the first observations begin, we require the same orient to be used throughout so that we can sample the faint background and foreground contaminating populations well, without the need for parallel observations. All of our objects have been observed with HST ACS/WFC before as part of program 10394. However, these shallow observations (2 orbits) only reach the RGB and HB, features common to both old clusters and dwarf galaxies, and thus insufficient for SFH analysis ------------------------------------------------------------------------------------ 18020( 2) - 08-Aug-2025 17:17:37 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NAME-M31-EC1 EXT-CLUSTER, GLOBULAR RA=00H38M19.4900S, J2000 V = 17.6 CLUSTER DEC=+41D47'14.90" Reference Frame: ICRS 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 ------------------------------------------------------------------------------------------------------------------------------------ 2 NAME-M31-EC2 EXT-CLUSTER, GLOBULAR RA=00H42M55.0000S, J2000 V = 17.1 CLUSTER DEC=+43D57'28.00" Reference Frame: ICRS Extended: NO 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 ------------------------------------------------------------------------------------------------------------------------------------ 3 NAME-M31-EC4 EXT-CLUSTER, GLOBULAR RA=00H58M15.4200S, J2000 V = 18.84 CLUSTER DEC=+38D03'2.00" Reference Frame: ICRS 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 ------------------------------------------------------------------------------------------------------------------------------------ 18020( 2) - 08-Aug-2025 17:17:37 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18020( 2) - 08-Aug-2025 17:17:37 - [ 6] Visit: 01 (EC1-1-606) Visit Requirements: ORIENT 245D TO 255 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F606W 2 550 S PATTERN 1 1 1 S see below (4436 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 1 none 1 557.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 2 none 1 557.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 1 none 1 557.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 2 none 1 557.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 1 none 2 552.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 2 none 2 552.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 1 none 2 552.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 2 none 2 552.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 7] Visit: 02 (EC1-1-814) Visit Requirements: ORIENT -10D TO +10D FROM 01 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 1 S see below (4948 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1363.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1121.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1353.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1111.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 8] Visit: 03 (EC1-2-606) Visit Requirements: ORIENT -10D TO 10D FROM 01 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F606W 2 550 S PATTERN 1 1 1 S see below (4436 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 1 none 1 557.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 2 none 1 557.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 1 none 1 557.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 2 none 1 557.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 1 none 2 552.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 2 none 2 552.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 1 none 2 552.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 2 none 2 552.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 9] Visit: 04 (EC1-2-814) Visit Requirements: ORIENT -10D TO +10D FROM 01 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 1 S see below (4948 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1363.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1121.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1353.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1111.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 10] Visit: 05 (EC1-3-814) Visit Requirements: ORIENT -10D TO +10D FROM 01 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 1 S see below (4948 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1363.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1121.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1353.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1111.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 11] Visit: 06 (EC1-4-814) Visit Requirements: ORIENT -10D TO +10D FROM 01 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 1 1000 S PATTERN 2 1 1 S see below (2484 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 1242.0 S S NAME-M31-EC1 1 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 1242.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 12] Visit: 07 (EC2-1-606) Visit Requirements: ORIENT 240D TO 260 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F606W 2 550 S PATTERN 1 1 2 S see below (4436 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 1 none 1 557.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 2 none 1 557.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 1 none 1 557.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 2 none 1 557.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 1 none 2 552.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 2 none 2 552.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 1 none 2 552.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 2 none 2 552.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 13] Visit: 08 (EC2-2-606) Visit Requirements: ORIENT -10D TO +10D FROM 07 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F606W 2 550 S PATTERN 1 1 2 S see below (4436 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 1 none 1 557.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 2 none 1 557.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 1 none 1 557.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 2 none 1 557.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 1 none 2 552.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 2 none 2 552.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 1 none 2 552.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 2 none 2 552.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 14] Visit: 09 (EC2-1-814) Visit Requirements: ORIENT -10D TO +10D FROM 07 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 2 S see below (4948 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1242.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1242.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1232.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1232.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 15] Visit: 10 (EC2-2-814) Visit Requirements: ORIENT -10D TO +10D FROM 07 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 2 S see below (4948 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1242.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1242.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1232.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1232.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 16] Visit: 11 (EC2-3-814) Visit Requirements: ORIENT -10D TO +10D FROM 07 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 2 S see below (4948 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1242.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1242.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1232.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1232.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 17] Visit: 12 (EC2-4-814) Visit Requirements: ORIENT -10D TO +10D FROM 07 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 1 1000 S PATTERN 2 1 2 S see below (2484 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 1242.0 S S NAME-M31-EC2 1 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 1242.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 18] Visit: 13 (EC4-1-606) Visit Requirements: ORIENT 245D TO 255 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F606W 2 550 S PATTERN 1 1 4 S see below (4420 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 1 none 1 555.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 2 none 1 555.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 1 none 1 555.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 2 none 1 555.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 1 none 2 550.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 2 none 2 550.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 1 none 2 550.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 2 none 2 550.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 19] Visit: 14 (EC4-2-606) Visit Requirements: ORIENT -10D TO +10D FROM 13 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F606W 2 550 S PATTERN 1 1 4 S see below (4420 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 1 none 1 555.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 1 none 2 none 1 555.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 1 none 1 555.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 2 none 2 none 1 555.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 1 none 2 550.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 3 none 2 none 2 550.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 1 none 2 550.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F606W 4 none 2 none 2 550.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 20] Visit: 15 (EC4-1-814) Visit Requirements: ORIENT -10D TO +10D FROM 13 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 4 S see below (4932 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1238.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1238.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1228.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1228.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 21] Visit: 16 (EC4-2-814) Visit Requirements: ORIENT -10D TO +10D FROM 13 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 4 S see below (4932 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1238.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1238.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1228.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1228.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 22] Visit: 17 (EC4-3-814) Visit Requirements: ORIENT -10D TO +10D FROM 13 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 2 1000 S PATTERN 2 1 4 S see below (4932 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 1 none 1 1238.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 1 none 2 none 1 1238.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 1 none 2 1228.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 2 none 2 none 2 1228.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 23] Visit: 18 (EC4-4-814) Visit Requirements: ORIENT -10D TO +10D FROM 13 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 NAME-M31-EC WFC3/UVI ACCUM UVIS1 F814W 1 1000 S PATTERN 2 1 4 S see below (2476 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 | ------------------------------------------------------------------------------------------------------------------------------------ NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 1 none none none 1 1238.0 S S NAME-M31-EC4 1 WFC3/UVI ACCUM UVIS1 F814W 2 none none none 1 1238.0 S S 18020( 2) - 08-Aug-2025 17:17:37 - [ 24] Summary Form for Proposal 18020 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT -10D TO +10D FROM 01, ORIENT -10D TO +10D FROM 07, ORIENT -10D TO +10D FROM 13, ORIENT -10D TO 10D FROM 01, ORIENT 240D TO 260 D, ORIENT 245D TO 255 D, PATTERN 1 1, PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NAME-M31-EC1, NAME-M31-EC2, NAME-M31-EC4 ------------------------------------------------------------------------------------------------------------------------------------