18128( 6) - 13-Nov-2025 12:57:31 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18128 Version: 6 Check-in Time: 13-Nov-2025 12:57:31 STScI Edit Number: 2 Title Search for an Intermediate-Mass Black Hole in Globular Cluster 47 Tuc ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Dana Ioana Casetti Southern Connecticut State University Y CoI: Dr. Terrence M. Girard Southern Connecticut State University N CoI: Dr. Roberto Baena-Galle International University of La Rioja N CoI: Dr. Holger Baumgardt University of Queensland N CoI: Ms. Arshia Anjum University of Queensland N ------------------------------------------------------------------------------------ Abstract Intermediate-Mass Black Holes (IMBHs), with masses between ~100 and 100, 000 solar masses, are expected to exist at the cores of Globular Clusters (GCs), but their existence has yet to be decisively confirmed observationally. Predictions suggest the influence of an IMBH would be limited to the central few arcsec of the GC core, an observationally challenging environment. It is here proposed to obtain highly precise proper motions at the core of 47 Tuc (NGC 104) in an effort to detect an IMBH. Existing archival WFPC2 observations for this cluster provide ideal first-epoch material that, when combined with the proposed new WFC3 observations, will provide an unprecedented 26-yr baseline for space-based, stellar proper motions. The expected relative proper-motion uncertainties will be on the order of 4 to 10 microarcsec/yr. The presence of an IMBH will be made via the detection of fast-moving stars at the GC center, i.e., orbital motion that would otherwise exceed the GC's escape velocity in the absence of an IMBH, along with detailed fitting of the observed velocity-dispersion profile with a theoretical mass-distribution model. ------------------------------------------------------------------------------------ Observations Description ------------------------ Second-epoch WFC3-UVIS images of the core of 47 Tuc (NGC 104) for relative proper-motion analysis. Observations consist of F555W and F814W paired exposures, dithered as: 15 UVIS 2K-subarray pointings (8pt dither + 0.2" Y-offset 7pt dither, as recommended in ISR WFC3 2020-07), and 6 UVIS full-frame pointings (6-pt dither, as recommended in ISR WFC3 2020-07). All exposures are 220-sec duration, with 12-electron FLASH. Cluster center is roughly positioned (via POSTARGs) at geometric center of UVIS 2K-subarray C, in all exposures. These exposures are split between two 3-orbit visits with a SAME-ORI-AS linkage. ------------------------------------------------------------------------------------ 18128( 6) - 13-Nov-2025 12:57:31 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-104 STELLAR CLUSTER, RA=00H24M5.3590S, J2000 V = 4.09 GLOBULAR CLUSTER DEC=-72D04'53.20" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.001137601772603942 -0.002529999915168446 2.32E-4 ------------------------------------------------------------------------------------------------------------------------------------ 18128( 6) - 13-Nov-2025 12:57:31 - [ 3] 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 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.4, 8.7; GS S C-SUB S) ACQ SCENARIO ONEB1O3 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.4, 8.7 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.4894, 9.0341 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.4894, 9.0341 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.5785, 8.8908 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC-104 WFC3/UVI ACCUM UVIS-FIX F555W FLASH=12 1 220 S (220 POS TARG 39.9, 33.1 S S) ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC-104 WFC3/UVI ACCUM UVIS-FIX F814W FLASH=12 1 220 S (220 POS TARG 39.9, 33.1 S S) ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.5785, 8.8908 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.6679, 9.2249 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.6679, 9.2249 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.7173, 9.0591 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.7173, 9.0591 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC-104 WFC3/UVI ACCUM UVIS-FIX F814W FLASH=12 1 220 S (220 POS TARG 39.9927, S S) 33.4376 ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC-104 WFC3/UVI ACCUM UVIS-FIX F555W FLASH=12 1 220 S (220 POS TARG 39.9927, S S) 33.4376 ------------------------------------------------------------------------------------------------------------------------------------ 18128( 6) - 13-Nov-2025 12:57:31 - [ 4] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.8067, 9.3932 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.8067, 9.3932 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.8958, 9.2101 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 18 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.8958, 9.2101 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 19 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 10.0644, 9.3902 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC-104 WFC3/UVI ACCUM UVIS-FIX F555W FLASH=12 1 220 S (220 POS TARG 40.0851, S S) 33.2978 ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC-104 WFC3/UVI ACCUM UVIS-FIX F814W FLASH=12 1 220 S (220 POS TARG 40.0851, S S) 33.2978 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 1 N/A S 2C-SUB NGC-104 2 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 1 N/A S 2C-SUB NGC-104 3 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 1 N/A S 2C-SUB NGC-104 4 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 1 N/A S 2C-SUB NGC-104 5 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 1 N/A S 2C-SUB NGC-104 6 WFC3/UVI ACCUM UVIS-FIX F555W none none none none 1 N/A S NGC-104 7 WFC3/UVI ACCUM UVIS-FIX F814W none none none none 1 N/A S NGC-104 8 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 2 N/A S 2C-SUB NGC-104 9 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 2 N/A S 2C-SUB NGC-104 10 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 2 N/A S 2C-SUB 18128( 6) - 13-Nov-2025 12:57:31 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 11 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 2 N/A S 2C-SUB NGC-104 12 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 2 N/A S 2C-SUB NGC-104 13 WFC3/UVI ACCUM UVIS-FIX F814W none none none none 2 N/A S NGC-104 14 WFC3/UVI ACCUM UVIS-FIX F555W none none none none 2 N/A S NGC-104 15 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 3 N/A S 2C-SUB NGC-104 16 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 3 N/A S 2C-SUB NGC-104 17 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 3 N/A S 2C-SUB NGC-104 18 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 3 N/A S 2C-SUB NGC-104 19 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 3 N/A S 2C-SUB NGC-104 20 WFC3/UVI ACCUM UVIS-FIX F555W none none none none 3 N/A S NGC-104 21 WFC3/UVI ACCUM UVIS-FIX F814W none none none none 3 N/A S 18128( 6) - 13-Nov-2025 12:57:31 - [ 6] Visit: 02 Visit Requirements: SAME ORIENT AS 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 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 10.0644, S C-SUB S) 9.3902; GS ACQ SCENARIO ONEB1O3 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.4, 8.9 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.4, 8.9 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.4894, 9.2341 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.4894, 9.2341 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC-104 WFC3/UVI ACCUM UVIS-FIX F814W FLASH=12 1 220 S (220 POS TARG 40.1382, S S) 33.6130 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC-104 WFC3/UVI ACCUM UVIS-FIX F555W FLASH=12 1 220 S (220 POS TARG 40.1382, S S) 33.6130 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.5785, 9.0908 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.5785, 9.0908 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.6679, 9.4249 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.6679, 9.4249 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.7173, 9.2591 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC-104 WFC3/UVI ACCUM UVIS-FIX F555W FLASH=12 1 220 S (220 POS TARG 40.2305, S S) 33.4732 ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC-104 WFC3/UVI ACCUM UVIS-FIX F814W FLASH=12 1 220 S (220 POS TARG 40.2305, S S) 33.4732 18128( 6) - 13-Nov-2025 12:57:31 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.7173, 9.2591 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.8100, 9.5967 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.8100, 9.5967 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 18 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F555W FLASH=12 1 220 S (220 POS TARG 9.9024, 9.4158 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 19 NGC-104 WFC3/UVI ACCUM UVIS2-2K2 F814W FLASH=12 1 220 S (220 POS TARG 9.9024, 9.4158 S C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC-104 WFC3/UVI ACCUM UVIS-FIX F814W FLASH=12 1 220 S (220 POS TARG 40.4024, S S) 33.6171 ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC-104 WFC3/UVI ACCUM UVIS-FIX F555W FLASH=12 1 220 S (220 POS TARG 40.4024, S S) 33.6171 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 1 N/A S 2C-SUB NGC-104 2 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 1 N/A S 2C-SUB NGC-104 3 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 1 N/A S 2C-SUB NGC-104 4 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 1 N/A S 2C-SUB NGC-104 5 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 1 N/A S 2C-SUB NGC-104 6 WFC3/UVI ACCUM UVIS-FIX F814W none none none none 1 N/A S NGC-104 7 WFC3/UVI ACCUM UVIS-FIX F555W none none none none 1 N/A S NGC-104 8 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 2 N/A S 2C-SUB NGC-104 9 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 2 N/A S 2C-SUB 18128( 6) - 13-Nov-2025 12:57:31 - [ 8] 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 10 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 2 N/A S 2C-SUB NGC-104 11 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 2 N/A S 2C-SUB NGC-104 12 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 2 N/A S 2C-SUB NGC-104 13 WFC3/UVI ACCUM UVIS-FIX F555W none none none none 2 N/A S NGC-104 14 WFC3/UVI ACCUM UVIS-FIX F814W none none none none 2 N/A S NGC-104 15 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 3 N/A S 2C-SUB NGC-104 16 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 3 N/A S 2C-SUB NGC-104 17 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 3 N/A S 2C-SUB NGC-104 18 WFC3/UVI ACCUM UVIS2-2K F555W none none none none 3 N/A S 2C-SUB NGC-104 19 WFC3/UVI ACCUM UVIS2-2K F814W none none none none 3 N/A S 2C-SUB NGC-104 20 WFC3/UVI ACCUM UVIS-FIX F814W none none none none 3 N/A S NGC-104 21 WFC3/UVI ACCUM UVIS-FIX F555W none none none none 3 N/A S 18128( 6) - 13-Nov-2025 12:57:31 - [ 9] Summary Form for Proposal 18128 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-FIX, UVIS2-2K2C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=12 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO ONEB1O3, POS TARG 10.0644, 9.3902, POS TARG 39.9, 33.1, POS TARG 39.9927, 33.4376, POS TARG 40.0851, 33.2978, POS TARG 40.1382, 33.6130, POS TARG 40.2305, 33.4732, POS TARG 40.4024, 33.6171, POS TARG 9.4, 8.7, POS TARG 9.4, 8.9, POS TARG 9.4894, 9.0341, POS TARG 9.4894, 9.2341, POS TARG 9.5785, 8.8908, POS TARG 9.5785, 9.0908, POS TARG 9.6679, 9.2249, POS TARG 9.6679, 9.4249, POS TARG 9.7173, 9.0591, POS TARG 9.7173, 9.2591, POS TARG 9.8067, 9.3932, POS TARG 9.8100, 9.5967, POS TARG 9.8958, 9.2101, POS TARG 9.9024, 9.4158, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC-104 ------------------------------------------------------------------------------------------------------------------------------------