Assigned ID: 456 ----- Attempting Submission 1 (Fri Feb 24 16:10:54 GMT 2012) ----- ----- Attempting Submission 2 (Fri Feb 24 16:30:31 GMT 2012) ----- ----- Attempting Submission 1 (Mon Jul 16 10:47:08 GMT 2012) ----- The warning just remind that a parallel observation is longer than the primary observation, but this is not a problem, it was done to minimize the unused visibility We have discovered that Terzan5, a stellar system in the Galactic bulge, harbors two stellar populations with different iron content (Delta[Fe/H]~0.5 dex) and possibly different ages (Ferraro et al. 2009, Nature 462, 483). Moreover, the observed chemical patterns (Origlia et al. 2011, ApJ 726, L20) significantly differ from those observed in any known genuine GC. These evidences demonstrate that, similarly to omega Centauri in the halo, Terzan5 is NOT a genuine globular cluster (GC), but a stellar system that was able to retain the gas ejected by violent supernova (SN) explosions. Indeed the striking chemical similarity with the bulge stars suggests that Terzan5 and the Galactic bulge shared the same star formation and chemical enrichment processes, driven by an exceptional amount of SNeII explosions (this is also the key to understand the origin of the extraordinary population of millisecond pulsars in Terzan5). A quite intriguing scenario is emerging from these observations: Terzan5 could be the relic of one of the massive clumps that contributed (through strong dynamical interactions with other pre-formed and internally-evolved sub-structures) to the formation of the Galactic bulge. Here we propose to use the WFC3 to accurately measure the age of the two populations directly from the main sequence turn-off luminosities. Precisely dating the first and second burst of star formation is a crucial step for the correct reconstruction of the evolutionary history of Terzan5, with a significant impact on our comprehension of the formation processes of the Milky Way bulge and, more in general, of galactic spheroids. The observations are organized in three visits: VISIT 1- Second epoch ACS optical observations for proper motion measures: 2 orbits. In order to exactly duplicate the observations secured in Prop GO9799 - PI Rich, we adopted the WFC1 aperture and the same ORIENation as in those images. In each orbit we require one short exposure (50sec in F606W and 10 sec in F814W) and 5 long exposures (t=365sec each). We adopted an ACS-DITHER-BOX pattern. In each orbit a parallel WFC3-IR (in F110W and F160W) image with exposure time of t=300sec is also required. VISIT 2 and VISIT 3- Deep WFC3-IR observations (4 orbits for each visit) with same ORIENTation. We required 4 orbits in each of the two selected filters (F110W and F160W). In each orbit we require 8 exposures performed with SAMP-SEQ=STEP50 and NSAMP=11. We adopted a dither pattern already succesfully tested in previous observations. For each orbit we placed a parallel ACS-WFC exposure (alternatively in F606W and F814W). RESOLVED STELLAR POPULATIONS 12 false 0.0 0.0 false false false false SUPPORTED STELLAR CLUSTER GLOBULAR CLUSTER J2000 J2000 STELLAR CLUSTER GLOBULAR CLUSTER J2000 J2000 WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F110W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W 1342434930784 The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. /Users/francesco/lavoro/proposal/hst20/phase2/OP-cache/ter5_6-v01.xml (Tic-Visit :proposal-id 12933 :visit-id "01" :proposal-version -1 :trans-version "20120604" :date "16-Jul-2012 12:35:30.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 3967760 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12933 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12933 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2907 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3244 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12933 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2840 :al-overhead-at-end 0 :internal-dur-at-end 1037 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3244 :pcs-gap 0 ) true 2 0 1342434938684 /Users/francesco/lavoro/proposal/hst20/phase2/OP-cache/ter5_6-v02.xml The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12933 :visit-id "02" :proposal-version -1 :trans-version "20120604" :date "16-Jul-2012 12:35:37.0" :trans-errors '(:WARNINGS 3 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 7822048 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12933 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12933 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2911 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3244 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12933 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3020 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3244 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12933 :visit-id "02" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3020 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3244 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12933 :visit-id "02" :orbit-number 4 :pcs-time 222 :si-vis-utilization 3020 :al-overhead-at-end 0 :internal-dur-at-end 1018 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3244 :pcs-gap 0 ) true 4 0 1342434945884 /Users/francesco/lavoro/proposal/hst20/phase2/OP-cache/ter5_6-v03.xml The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. 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