17929( 2) - 30-Jan-2025 13:08:52 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17929 Version: 2 Check-in Time: 30-Jan-2025 13:08:52 STScI Edit Number: 0 Title The true nature of Glimpse-C01: another star cluster hosting multi-age populations? ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Mario Cadelano University of Bologna Y CoI: Ms. Lanfranco Chiappino University of Bologna N CoI: Dr. Chiara Crociati University of Edinburgh, Institute for N Astronomy CoI: Dr. Emanuele Dalessandro INAF - Osservatorio di Astrofisica e N Scienza dello Spazio CoI: Prof. Francesco R. Ferraro University of Bologna N CoI: Camilla Giusti University of Bologna N CoI: Prof. Barbara Lanzoni University of Bologna N CoI: Mrs. Silvia Leanza University of Bologna N CoI: Ms. Martina Loriga University of Bologna N CoI: Dr. Davide Massari INAF - Osservatorio di Astrofisica e N Scienza dello Spazio CoI: Dr. Livia Origlia INAF - Osservatorio di Astrofisica e N Scienza dello Spazio CoI: Dr. Cristina Pallanca University of Bologna N CoI: Dr. Enrico Vesperini Indiana University System N ------------------------------------------------------------------------------------ Abstract Of the ~150 old globular clusters in the Milky Way, there are 3 outstanding systems that defy the globular cluster classification and show the presence of multi-age and multi-iron populations: Omega Centauri in the Galactic halo, Terzan 5 and Liller 1 in the bulge, which may be fossil witnesses to the past evolution and assembly of the Milky Way. The discovery of such systems provides a unique opportunity to gain deeper insights into the assembly history of the Milky Way. Analysis of archival HST observations of the Glimpse-C01 cluster suggests that it may be the fourth member of this emerging class of exotic clusters hosting multi-age, multi-iron stellar populations, and the first to be located in the Milky Way disk. To confirm this scenario, we require a second epoch of ACS and WFC3 observations to measure the proper motions of the stars in the direction of the cluster, which are the fundamental ingredient for distinguishing cluster members from field interlopers. Given the extreme crowding conditions and the severe reddening in the direction of the cluster, the proposed goal can be achieved by exploiting the high-resolution and stable astrometric optical/near-IR capabilities of the ACS/WFC and WFC3/IR cameras, while JWST observations would quickly saturate due to the target's relatively small distance from the Sun. The observations will be used to analyse and directly measure the age(s) of the stellar population(s) for the first time, and to reconstruct the cluster orbit in the Milky Way potential field, thus shedding light on its origin, the possible formation mechanism of its multi-age populations, and the role of the cluster in the Milky Way assembly history. ------------------------------------------------------------------------------------ 17929( 2) - 30-Jan-2025 13:08:52 - [ 2] Observations Description ------------------------ The goal of the proposal is to sample the stellar population of the cluster Glimpse-C01 using a combination of ACS/WFC and WFC3/IR observations. Specifically, we plan to organize the observations into a single visit of three HST orbits. The first orbit will be dedicated to WFC3/IR observations. It consists of a combination of images taken in the F110W and F160W filters with SAMP-SEQ=STEP25 and NSAMP=9-14. We use the IR-FIX aperture and apply small shifts among different exposures using POS_TARG. The second and third orbits will be dedicated to ACS/WFC observations. We plan to obtain 3 exposures of 693-712 s in each orbit, using the ACS-WFC-DITHER-LINE pattern and the WFC-FIX aperture. ------------------------------------------------------------------------------------ 17929( 2) - 30-Jan-2025 13:08:52 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GLIMPSE-C01 STELLAR CLUSTER, RA=18H48M49.7000S, J2000 V = 20 GLOBULAR CLUSTER DEC=-01D29'50.00" 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 ------------------------------------------------------------------------------------------------------------------------------------ 17929( 2) - 30-Jan-2025 13:08:52 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 3.034 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.29 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17929( 2) - 30-Jan-2025 13:08:52 - [ 5] Visit: 04 (visit 1 - step 25) 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 GLIMPSE-C01 WFC3/IR MULTIAC IR-FIX F160W SAMP-SEQ=STEP25, NSAMP=11 1 DEF CUM (174.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 GLIMPSE-C01 WFC3/IR MULTIAC IR-FIX F110W SAMP-SEQ=STEP25, NSAMP=14 1 DEF CUM (249.234 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 GLIMPSE-C01 WFC3/IR MULTIAC IR-FIX F160W SAMP-SEQ=STEP25, NSAMP=11 1 DEF POS TARG 1, 1 CUM (174.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 GLIMPSE-C01 WFC3/IR MULTIAC IR-FIX F110W SAMP-SEQ=STEP25, NSAMP=14 1 DEF POS TARG 1, 1 CUM (249.234 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 GLIMPSE-C01 WFC3/IR MULTIAC IR-FIX F160W SAMP-SEQ=STEP25, NSAMP=10 1 DEF POS TARG 2, 2 CUM (149.232 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 GLIMPSE-C01 WFC3/IR MULTIAC IR-FIX F110W SAMP-SEQ=STEP25, NSAMP=13 1 DEF POS TARG 2, 2 CUM (224.234 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 GLIMPSE-C01 WFC3/IR MULTIAC IR-FIX F160W SAMP-SEQ=STEP25, NSAMP=9 1 DEF POS TARG 3, 3 CUM (124.232 S) ------------------------------------------------------------------------------------------------------------------------------------ 8 GLIMPSE-C01 WFC3/IR MULTIAC IR-FIX F110W SAMP-SEQ=STEP25, NSAMP=12 1 DEF POS TARG 3, 3 CUM (199.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 GLIMPSE-C01 ACS/WFC ACCUM WFC-FIX F814W 1 693 S PATTERN 1 9 (2079 S) ------------------------------------------------------------------------------------------------------------------------------------ 10 GLIMPSE-C01 ACS/WFC ACCUM WFC-FIX F814W 1 712 S PATTERN 1 10 (2136 S) ------------------------------------------------------------------------------------------------------------------------------------ 17929( 2) - 30-Jan-2025 13:08:52 - [ 6] 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 | ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GLIMPSE-C01 1 WFC3/IR MULTIAC IR-FIX F160W none none none none 1 N/A CUM GLIMPSE-C01 2 WFC3/IR MULTIAC IR-FIX F110W none none none none 1 N/A CUM GLIMPSE-C01 3 WFC3/IR MULTIAC IR-FIX F160W none none none none 1 N/A CUM GLIMPSE-C01 4 WFC3/IR MULTIAC IR-FIX F110W none none none none 1 N/A CUM GLIMPSE-C01 5 WFC3/IR MULTIAC IR-FIX F160W none none none none 1 N/A CUM GLIMPSE-C01 6 WFC3/IR MULTIAC IR-FIX F110W none none none none 1 N/A CUM GLIMPSE-C01 7 WFC3/IR MULTIAC IR-FIX F160W none none none none 1 N/A CUM GLIMPSE-C01 8 WFC3/IR MULTIAC IR-FIX F110W none none none none 1 N/A CUM GLIMPSE-C01 9 ACS/WFC ACCUM WFC-FIX F814W 1 none none none 2 N/A GLIMPSE-C01 9 ACS/WFC ACCUM WFC-FIX F814W 2 none none none 2 N/A GLIMPSE-C01 9 ACS/WFC ACCUM WFC-FIX F814W 3 none none none 2 N/A GLIMPSE-C01 10 ACS/WFC ACCUM WFC-FIX F814W 1 none none none 3 N/A GLIMPSE-C01 10 ACS/WFC ACCUM WFC-FIX F814W 2 none none none 3 N/A GLIMPSE-C01 10 ACS/WFC ACCUM WFC-FIX F814W 3 none none none 3 N/A 17929( 2) - 30-Jan-2025 13:08:52 - [ 7] Summary Form for Proposal 17929 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR-FIX, WFC-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=10, NSAMP=11, NSAMP=12, NSAMP=13, NSAMP=14, NSAMP=9, SAMP-SEQ=STEP25 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 10, PATTERN 1 9, POS TARG 1, 1, POS TARG 2, 2, POS TARG 3, 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W, F160W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GLIMPSE-C01 ------------------------------------------------------------------------------------------------------------------------------------