15231( 3) - 13-Mar-2019 13:42:55 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15231 Version: 3 Check-in Time: 13-Mar-2019 13:42:55 STScI Edit Number: 1 Title Searching for fossil fragments of the Galactic bulge formation process ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Francesco R. Ferraro Universita di Bologna Y CoI: Dr. Cristina Pallanca Universita di Bologna N CoI: Dr. Barbara Lanzoni Universita di Bologna N CoI: Dr. Sara Saracino Universita di Bologna N CoI: Dr. Alessio Mucciarelli Universita di Bologna N CoI: Dr. Livia Origlia INAF, Osservatorio Astronomico di Bologna N CoI: Dr. Emanuele Dalessandro INAF, Osservatorio di Astrofisica e N Scienza dello Spazio di B CoI: Dr. R. Michael Rich University of California - Los Angeles N CoI: Dr. Davide Massari Kapteyn Astronomical Institute N CoI: Mr. Mario Cadelano Universita di Bologna N CoI: Dr. Elena Valenti European Southern Observatory - Germany N CoI: Mrs. Silvia Raso Universita di Bologna N ------------------------------------------------------------------------------------ Abstract We have discovered that the stellar system Terzan5 (Ter5) in the Galactic bulge harbors stellar populations with very different IRON content (delta[Fe/H]~1 dex, Ferraro+09, Nature 462, 483) and AGES (12 Gyr and 4.5 Gyr for the sub-solar and super-solar metallicity populations, respectively, Ferraro+16, ApJ, 828, 75). This evidence demonstrates that Ter5 is not a globular cluster, and identifies it as (1) a site in the Galactic bulge where recent star formation occurred, and (2) the remnant of a massive system able to retain the iron-enriched gas ejected by violent supernova explosions. The striking chemical similarity between Ter5 and the bulge opens the fascinating possibility that we discovered the fossil remnant of a pristine massive structure that could have contributed to the Galactic bulge assembly. Prompted by this finding, here we propose to secure deep HST optical observations for the bulge stellar system Liller1, that shows a similar complexity as Ter5, with evidence of two stellar populations with different iron content. The immediate goal is to properly explore the main sequence turnoff region of the system for unveiling possible splits due to stellar populations of different ages. As demonstrated by our experience with Ter5, the requested HST observations, in combination with the K-band diffraction limited images that we already secured with GeMS-Gemini, are essential to achieve this goal. The project will allow us to establish if other fossil remnants of the bulge formation epoch do exist, thus probing that the merging of pre-evolved massive structures has been an important channel for the formation of the Galactic bulge. ------------------------------------------------------------------------------------ Observations Description ------------------------ We plan to secure optical images in two classical ACS passbands (F814W and 15231( 3) - 13-Mar-2019 13:42:55 - [ 2] F606W) of the stellar system Liller1 in the galactic bulge. The observations are organized in just one visit: 3 orbits are needed to secure 6 exposures (each 1300 sec -long) in the F606W filter and 2 orbits to secure 6 exposures (each ~850 sec-long) in the F814W filter. All the exposures have been dithered by using appropriate offsets. Parallel observation with the WFC3 in the F606W, F814W, F110W and F160W filters are also planned in order to sample the bulge field population in the region surrounding the cluster. ------------------------------------------------------------------------------------ 15231( 3) - 13-Mar-2019 13:42:55 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LILLER1 STELLAR CLUSTER, RA=17H33M24.5600S, J2000 V = 28 GLOBULAR CLUSTER DEC=-33D23'22.40" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 15231( 3) - 13-Mar-2019 13:42:55 - [ 4] Visit: 03 (liller1) 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 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1260 S PAR 2 WITH 1 (1260 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 1349 S S (1349 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1260 S POS TARG -0.099, -0.165; (1260 S) PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F606W 1 1349 S S (1349 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1361 S POS TARG 0.059, -0.095; (1361 S) PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFC3/IR MULTIAC IR F160W NSAMP=14, SAMP-SEQ=STEP200 1 DEF CUM (1399.231 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1361 S POS TARG 0.218, -0.024; (1361 S) PAR 8 WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 ANY WFC3/IR MULTIAC IR F110W NSAMP=14, SAMP-SEQ=STEP200 1 DEF CUM (1399.231 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1360 S POS TARG 0.158, 0.07; (1360 S) PAR 10 WITH 9 ------------------------------------------------------------------------------------------------------------------------------------ 10 ANY WFC3/UVI ACCUM UVIS1 F606W 1 1392 S S (1392 S) ------------------------------------------------------------------------------------------------------------------------------------ 11 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1360 S POS TARG 0.099, 0.165; (1360 S) PAR 12 WITH 11 ------------------------------------------------------------------------------------------------------------------------------------ 12 ANY WFC3/UVI ACCUM UVIS1 F606W 1 1392 S S (1392 S) ------------------------------------------------------------------------------------------------------------------------------------ 13 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 836 S (836 POS TARG -0.059, 0.095; S) PAR 14 WITH 13 ------------------------------------------------------------------------------------------------------------------------------------ 15231( 3) - 13-Mar-2019 13:42:55 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 14 ANY WFC3/UVI ACCUM UVIS1 F814W 1 865 S (865 S S) ------------------------------------------------------------------------------------------------------------------------------------ 15 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 836 S (836 POS TARG -0.218, 0.024; S) PAR 16 WITH 15 ------------------------------------------------------------------------------------------------------------------------------------ 16 ANY WFC3/UVI ACCUM UVIS1 F814W 1 865 S (865 S S) ------------------------------------------------------------------------------------------------------------------------------------ 17 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 837 S (837 POS TARG -0.158, -0.07; S) PAR 18 WITH 17 ------------------------------------------------------------------------------------------------------------------------------------ 18 ANY WFC3/UVI ACCUM UVIS1 F814W 1 865 S (865 S S) ------------------------------------------------------------------------------------------------------------------------------------ 19 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 855 S (855 POS TARG -0.158, -0.11; S) PAR 20 WITH 19 ------------------------------------------------------------------------------------------------------------------------------------ 20 ANY WFC3/UVI ACCUM UVIS1 F814W 1 864 S (864 S S) ------------------------------------------------------------------------------------------------------------------------------------ 21 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 855 S (855 POS TARG -0.099, 0.052; S) PAR 22 WITH 21 ------------------------------------------------------------------------------------------------------------------------------------ 22 ANY WFC3/UVI ACCUM UVIS1 F814W 1 864 S (864 S S) ------------------------------------------------------------------------------------------------------------------------------------ 23 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 854 S (854 POS TARG -0.040, 0.214; S) PAR 24 WITH 23 ------------------------------------------------------------------------------------------------------------------------------------ 24 ANY WFC3/UVI ACCUM UVIS1 F814W 1 864 S (864 S 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 | ------------------------------------------------------------------------------------------------------------------------------------ LILLER1 1 ACS/WFC ACCUM WFC1 F606W none none none none 1 N/A ANY 2 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S LILLER1 3 ACS/WFC ACCUM WFC1 F606W none none none none 1 N/A ANY 4 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S LILLER1 5 ACS/WFC ACCUM WFC1 F606W none none none none 2 N/A 15231( 3) - 13-Mar-2019 13:42:55 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ ANY 6 WFC3/IR MULTIAC IR F160W none none none none 2 N/A CUM LILLER1 7 ACS/WFC ACCUM WFC1 F606W none none none none 2 N/A ANY 8 WFC3/IR MULTIAC IR F110W none none none none 2 N/A CUM LILLER1 9 ACS/WFC ACCUM WFC1 F606W none none none none 3 N/A ANY 10 WFC3/UVI ACCUM UVIS1 F606W none none none none 3 N/A S LILLER1 11 ACS/WFC ACCUM WFC1 F606W none none none none 3 N/A ANY 12 WFC3/UVI ACCUM UVIS1 F606W none none none none 3 N/A S LILLER1 13 ACS/WFC ACCUM WFC1 F814W none none none none 4 N/A ANY 14 WFC3/UVI ACCUM UVIS1 F814W none none none none 4 N/A S LILLER1 15 ACS/WFC ACCUM WFC1 F814W none none none none 4 N/A ANY 16 WFC3/UVI ACCUM UVIS1 F814W none none none none 4 N/A S LILLER1 17 ACS/WFC ACCUM WFC1 F814W none none none none 4 N/A ANY 18 WFC3/UVI ACCUM UVIS1 F814W none none none none 4 N/A S LILLER1 19 ACS/WFC ACCUM WFC1 F814W none none none none 5 N/A ANY 20 WFC3/UVI ACCUM UVIS1 F814W none none none none 5 N/A S LILLER1 21 ACS/WFC ACCUM WFC1 F814W none none none none 5 N/A ANY 22 WFC3/UVI ACCUM UVIS1 F814W none none none none 5 N/A S LILLER1 23 ACS/WFC ACCUM WFC1 F814W none none none none 5 N/A ANY 24 WFC3/UVI ACCUM UVIS1 F814W none none none none 5 N/A S 15231( 3) - 13-Mar-2019 13:42:55 - [ 7] Visit: 04 (liller1) 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 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1260 S PAR 2 WITH 1 (1260 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFC3/UVI ACCUM UVIS1 F606W 1 1349 S S (1349 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1260 S POS TARG -0.099, -0.165; (1260 S) PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFC3/UVI ACCUM UVIS1 F606W 1 1349 S S (1349 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1361 S POS TARG 0.059, -0.095; (1361 S) PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFC3/IR MULTIAC IR F160W NSAMP=14, SAMP-SEQ=STEP200 1 DEF CUM (1399.231 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1361 S POS TARG 0.218, -0.024; (1361 S) PAR 8 WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 ANY WFC3/IR MULTIAC IR F110W NSAMP=14, SAMP-SEQ=STEP200 1 DEF CUM (1399.231 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1360 S POS TARG 0.158, 0.07; (1360 S) PAR 10 WITH 9 ------------------------------------------------------------------------------------------------------------------------------------ 10 ANY WFC3/UVI ACCUM UVIS1 F606W 1 1392 S S (1392 S) ------------------------------------------------------------------------------------------------------------------------------------ 11 LILLER1 ACS/WFC ACCUM WFC1 F606W 1 1360 S POS TARG 0.099, 0.165; (1360 S) PAR 12 WITH 11 ------------------------------------------------------------------------------------------------------------------------------------ 12 ANY WFC3/UVI ACCUM UVIS1 F606W 1 1392 S S (1392 S) ------------------------------------------------------------------------------------------------------------------------------------ 13 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 836 S (836 POS TARG -0.059, 0.095; S) PAR 14 WITH 13 ------------------------------------------------------------------------------------------------------------------------------------ 15231( 3) - 13-Mar-2019 13:42:55 - [ 8] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 14 ANY WFC3/UVI ACCUM UVIS1 F814W 1 865 S (865 S S) ------------------------------------------------------------------------------------------------------------------------------------ 15 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 836 S (836 POS TARG -0.218, 0.024; S) PAR 16 WITH 15 ------------------------------------------------------------------------------------------------------------------------------------ 16 ANY WFC3/UVI ACCUM UVIS1 F814W 1 865 S (865 S S) ------------------------------------------------------------------------------------------------------------------------------------ 17 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 837 S (837 POS TARG -0.158, -0.07; S) PAR 18 WITH 17 ------------------------------------------------------------------------------------------------------------------------------------ 18 ANY WFC3/UVI ACCUM UVIS1 F814W 1 865 S (865 S S) ------------------------------------------------------------------------------------------------------------------------------------ 19 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 855 S (855 POS TARG -0.158, -0.11; S) PAR 20 WITH 19 ------------------------------------------------------------------------------------------------------------------------------------ 20 ANY WFC3/UVI ACCUM UVIS1 F814W 1 864 S (864 S S) ------------------------------------------------------------------------------------------------------------------------------------ 21 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 855 S (855 POS TARG -0.099, 0.052; S) PAR 22 WITH 21 ------------------------------------------------------------------------------------------------------------------------------------ 22 ANY WFC3/UVI ACCUM UVIS1 F814W 1 864 S (864 S S) ------------------------------------------------------------------------------------------------------------------------------------ 23 LILLER1 ACS/WFC ACCUM WFC1 F814W 1 854 S (854 POS TARG -0.040, 0.214; S) PAR 24 WITH 23 ------------------------------------------------------------------------------------------------------------------------------------ 24 ANY WFC3/UVI ACCUM UVIS1 F814W 1 864 S (864 S 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 | ------------------------------------------------------------------------------------------------------------------------------------ LILLER1 1 ACS/WFC ACCUM WFC1 F606W none none none none 1 N/A ANY 2 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S LILLER1 3 ACS/WFC ACCUM WFC1 F606W none none none none 1 N/A ANY 4 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S LILLER1 5 ACS/WFC ACCUM WFC1 F606W none none none none 2 N/A 15231( 3) - 13-Mar-2019 13:42:55 - [ 9] 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 | ------------------------------------------------------------------------------------------------------------------------------------ ANY 6 WFC3/IR MULTIAC IR F160W none none none none 2 N/A CUM LILLER1 7 ACS/WFC ACCUM WFC1 F606W none none none none 2 N/A ANY 8 WFC3/IR MULTIAC IR F110W none none none none 2 N/A CUM LILLER1 9 ACS/WFC ACCUM WFC1 F606W none none none none 3 N/A ANY 10 WFC3/UVI ACCUM UVIS1 F606W none none none none 3 N/A S LILLER1 11 ACS/WFC ACCUM WFC1 F606W none none none none 3 N/A ANY 12 WFC3/UVI ACCUM UVIS1 F606W none none none none 3 N/A S LILLER1 13 ACS/WFC ACCUM WFC1 F814W none none none none 4 N/A ANY 14 WFC3/UVI ACCUM UVIS1 F814W none none none none 4 N/A S LILLER1 15 ACS/WFC ACCUM WFC1 F814W none none none none 4 N/A ANY 16 WFC3/UVI ACCUM UVIS1 F814W none none none none 4 N/A S LILLER1 17 ACS/WFC ACCUM WFC1 F814W none none none none 4 N/A ANY 18 WFC3/UVI ACCUM UVIS1 F814W none none none none 4 N/A S LILLER1 19 ACS/WFC ACCUM WFC1 F814W none none none none 5 N/A ANY 20 WFC3/UVI ACCUM UVIS1 F814W none none none none 5 N/A S LILLER1 21 ACS/WFC ACCUM WFC1 F814W none none none none 5 N/A ANY 22 WFC3/UVI ACCUM UVIS1 F814W none none none none 5 N/A S LILLER1 23 ACS/WFC ACCUM WFC1 F814W none none none none 5 N/A ANY 24 WFC3/UVI ACCUM UVIS1 F814W none none none none 5 N/A S 15231( 3) - 13-Mar-2019 13:42:55 - [ 10] Summary Form for Proposal 15231 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, UVIS1, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=14, SAMP-SEQ=STEP200 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PAR 10 WITH 9, PAR 12 WITH 11, PAR 14 WITH 13, PAR 16 WITH 15, PAR 18 WITH 17, PAR 2 WITH 1, PAR 20 WITH 19, PAR 22 WITH 21, PAR 24 WITH 23, PAR 4 WITH 3, PAR 6 WITH 5, PAR 8 WITH 7, POS TARG -0.040, 0.214, POS TARG -0.059, 0.095, POS TARG -0.099, -0.165, POS TARG -0.099, 0.052, POS TARG -0.158, -0.07, POS TARG -0.158, -0.11, POS TARG -0.218, 0.024, POS TARG 0.059, -0.095, POS TARG 0.099, 0.165, POS TARG 0.158, 0.07, POS TARG 0.218, -0.024 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W, F160W, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, LILLER1 ------------------------------------------------------------------------------------------------------------------------------------