0 Assigned ID: 96 ----- Attempting Submission 1 (Tue Apr 04 11:53:01 GMT 2017) ----- 0 ----- Attempting Submission 1 (Mon Jul 17 16:50:59 GMT 2017) ----- ----- Attempting Submission 2 (Tue Jul 25 17:05:55 GMT 2017) ----- Pinpointing the Onset of Multiple Populations in Globular Clusters We have potentially pinpointed the onset of the multiple populations (MPs) phenomenon during our HST Cycle 23 program where we were looking for an abundance spreads in 12 massive LMC/SMC clusters with wide range of ages. All of the clusters have similar mass (~10^5 Msun), however, not all of the clusters were found to host MPs. From the observed sample, all clusters (five) above an age of 6 Gyr show clear signs of MPs in their post-main sequences (i.e., the RGB), while all clusters (seven) below this age do not show evidence of MPs. Such a relation with age is not expected in any scenario for the origin of MPs, and constitutes one of the most important findings in the field in recent years. One potential explanation for the observations is that MPs do exist within the young clusters, but only below a certain stellar mass limit. We propose to obtain deeper imaging of NGC 419, a 1.5 Gyr cluster that does not show MPs in its RGB (~1.6 Msun), in order to search for splitting along main sequence stars (~1 Msun and below) caused by the chemical anomalies. Based on stellar isochrones with MPs abundance variations, we expect to observe any main sequence splitting with an additional 8 orbits of exposure using our unique filter combination. Determining if a stellar mass limit exists for MPs would consistute a major step forward in the search for the origin of the multiple populations phenomenon. We propose to obtain imaging of 2 massive star clusters one within the LMC/SMC, and another one old galactic globular cluster spanning a wide range of ages (0.1 - 10 Gyr), in order to search for elemental abundance spreads and multiple populations. The clusters will be observed in the F343N, F336W and F438W WFC3/UVIS filters, which will provide accurate color-magnitude diagrams (CMD) for studies of these phenomena. A CMD for such a large range of stellar ages covers everything from red and very bright giants down to the main sequence stars of various brightness and colors. To reach our science goals, it is crucial not to saturate the bright giants by using a short exposure and to reach a sufficient depth beyond the main-sequence turn-off using long exposures. Therefore, for each cluster, a short exposure (observed in Cycle 23) and long exposures with CR-split in each filter are required. To cover the gap between the two WFC3/UVIS CCD chips, we use two dithered pointings. In order to maximize the overlap, we also require a specific orientation to match the orientation of those target clusters which have archival observations with the WFC3/UVIS. This orientation is specified in the Visit Orientation Requirement for these clusters/visits as follows: Visit1 - ngc419, Min=307, Max=307; Visit2 - ngc104 (47Tuc), Min=0, Min=1 Stellar Populations 6 false false false false false false SUPPORTED STELLAR CLUSTER GLOBULAR CLUSTER OPEN CLUSTER NO This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 STELLAR CLUSTER GLOBULAR CLUSTER This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 WFC3/UVIS Imaging No No F343N WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F343N WFC3/UVIS Imaging No No F438W The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15061 :visit-id "01" :proposal-version -1 :trans-version "20170613" :date "25-Jul-2017 11:16:42.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2021216 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15061 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15061 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2933 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3266 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15061 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3044 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3266 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15061 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3044 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3266 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15061 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 3044 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3266 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15061 :visit-id "01" :orbit-number 5 :pcs-time 222 :si-vis-utilization 3044 :al-overhead-at-end 121 :internal-dur-at-end 352 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3266 :pcs-gap 0 ) true 5 0 The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15061 :visit-id "02" :proposal-version -1 :trans-version "20170613" :date "25-Jul-2017 11:15:13.0" :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 1443728 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15061 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15061 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2932 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3266 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15061 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3044 :al-overhead-at-end 120 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3266 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15061 :visit-id "02" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3044 :al-overhead-at-end 116 :internal-dur-at-end 352 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3266 :pcs-gap 0 ) true 3 0 The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15061 :visit-id "03" :proposal-version -1 :trans-version "20170613" :date "25-Jul-2017 13:16:05.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1443728 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15061 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15061 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3229 :al-overhead-at-end 122 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3585 :pcs-gap 0 ) false 1 0