0 Assigned ID: 6226 ----- Attempting Submission 1 (Wed Apr 09 13:11:55 GMT 2025) ----- 0 ----- Attempting Submission 1 (Mon Aug 11 13:59:00 GMT 2025) ----- ----- Attempting Submission 2 (Sat Oct 18 15:31:52 GMT 2025) ----- ----- Attempting Submission 3 (Wed Nov 12 23:10:15 GMT 2025) ----- 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. 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. PI Dana I. Casetti: Over 25 years of experience as a research scientist in Galactic structure and kinematics. Responsible for measuring and compiling the most comprehensive, pre-Gaia catalog of absolute proper motions of globular clusters (with ~20 citations/year for 15 years), as well as the for measuring the first absolute proper motions in distant tidal streams and halo overdensities. Expertise in astrometry with photographic plates and large format CCDs (including SuprimeCam on Subaru). PI on HST AR proposal 15632, "Expanding HST's Astrometry Legacy: A Comprehensive Astrometric Calibration of WFPC2" which has produced an improved distortion correction map for this camera in three filters. An immediate outcome of this calibration is the new determination of Leo I proper motion, now a member of the polar alignment of Milky-Way satellite galaxies. Experience with applying AI and deep-learning (DL) techniques to WFPC2 astrometry. This pioneering technique developed by our group at Southern Connecticut State University yields improved astrometric precision of these WFPC2 exposures, which now offer 20-25 years baselines for proper-motion studies. An undergoing study led by Casetti that benefits from such newly processed WFPC2 exposures aims to measure the proper motions of six Andromeda satellites. One such satellite, And III has been recently measured and published (ApJ 2024, in press). Co-I Terrence M. Girard: Over 35 years experience in astronomy research including astrometry, relative and absolute proper-motion studies, and astrometric calibration of imagers. He has constructed data analysis pipelines for several major research projects, including the Yale/San Juan Southern Proper Motion program and the Solar Disk Sextant. Responsible for the construction of the largest (area and depth), most accurate, pre-Gaia astrometric catalog, the Southern Proper-Motion Catalog 4. Responsible for developing code and methodology for calibrating the WFPC2 camera (Co-I on HST AR 15632). Girard also worked recently on a project to recalibrate and reprocess the La Silla-QUEST Southern Hemisphere Supernova and Variability Surveys. These surveys employed the 10-square-degree QUEST camera (112 detectors, each 2400x600 pixels) at the prime focus of the 1.0-m ESO Schmidt Telescope at La Silla, Chile. Girard reworked and streamlined the reduction pipeline at Yale, incorporating the Gaia EDR3 for astrometric and photometric calibration, thus greatly improving the astrometric output products, in particular. This work also gave benefit to an ongoing project at Yale to do a full-survey coadd of the hundreds of repeated QUEST exposures over the entire southern sky. Girard joins the new effort to improve WFPC2 astrometry using DL techniques; he has generated WFPC2 simulated images and analyzed simulated and real WFPC2 images in order to test the precision of classical centering algorithms and the DL ones. He is also exploring and testing distortion solutions on the ACS-WF camera. Co-I Roberto Baena-Galle : He holds a PhD in astronomy (Univ. of Barcelona) and is also an electronic engineer (Univ. of Seville). He has expertis in the use of multiscalar transforms, such as wavelets and curvelets and into deconvolution algorithms to improve the spatial resolution of AO images. His professional career has developed in the field of digital image processing through the design and development of algorithms for image reconstruction, deconvolution and inverse problem solving. These tools have been applied to high resolution astronomical images, satellite reconstruction affected by atmospheric turbulence and medical images of the retina. Currently, he is working on the application of deep learning techniques on astronomical images, for example, CNNs and LSTMs to analyse and characterize light curves, for star centering in sub-sampled WFPC2 HST images, and for galaxy image denoising and deblurring. While he is now based at Universitad Iternacional de la Rioja (Spain) he has been a visiting faculty at Southern Connecticut State University for the past two years, with a total of three full semesters. Here he developed a collaboration with Casetti and Girard which has produced two refereed papers on deep-learning centering techniques for WFPC2. Co-I Holger Baumgardt is an expert on dynamical N-body simulations and is well known for his research on star clusters and the dynamics of stellar systems surrounding massive, central black holes. He has pioneered our understanding of if and where IMBHs have formed in the universe. Through N-body simulations, he and his collaborators were able to show that the repeated merging of stars in dense star clusters is a possible formation channel for IMBHs. He has also led efforts to search Galactic globular clusters for signs that they host IMBHs and has been a member of the team which in 2024 found an 8000 Msun IMBH in the globular cluster Omega Centauri. Co-I Arshia Anjum is a first year PhD student working on the dynamics of intermediate-mass black holes in globular clusters under the supervision of Holger Baumgardt. She uses Monte-Carlo codes to model stellar tidal disruptions and gravitational wave driven black hole mergers with IMBHs. She will run the simulations that will be compared to the observational data of 47 Tuc. Stellar Populations and the Interstellar Medium 6 false false false false true false false false false false SUPPORTED STELLAR CLUSTER GLOBULAR CLUSTER 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. J2000 J2000 WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F814W 1762967497252 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18128 :visit-id "01" :proposal-version -1 :trans-version "20250624" :date "12-Nov-2025 12:11:36.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2788368 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18128 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18128 :visit-id "01" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2710 :al-overhead-at-end 58 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3121 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18128 :visit-id "01" :orbit-number 2 :pcs-time 301 :si-vis-utilization 2701 :al-overhead-at-end 58 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3121 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18128 :visit-id "01" :orbit-number 3 :pcs-time 301 :si-vis-utilization 2645 :al-overhead-at-end 123 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3121 :pcs-gap 0 ) true 3 0 1762967490978 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18128 :visit-id "02" :proposal-version -1 :trans-version "20250624" :date "12-Nov-2025 12:11:30.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2788368 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18128 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18128 :visit-id "02" :orbit-number 1 :pcs-time 301 :si-vis-utilization 2701 :al-overhead-at-end 58 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3121 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18128 :visit-id "02" :orbit-number 2 :pcs-time 301 :si-vis-utilization 2710 :al-overhead-at-end 58 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3121 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18128 :visit-id "02" :orbit-number 3 :pcs-time 301 :si-vis-utilization 2636 :al-overhead-at-end 123 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3121 :pcs-gap 0 ) true 3 0