15061( 5) - 25-Jul-2017 17:48:41 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15061 Version: 5 Check-in Time: 25-Jul-2017 17:48:41 STScI Edit Number: 2 Title Pinpointing the Onset of Multiple Populations in Globular Clusters ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Nate Bastian Liverpool John Moores University Y CoI: Mr. Ivan Cabrera-Ziri Harvard University N CoI: Dr. Emanuele Dalessandro INAF, Osservatorio Astronomico di Bologna N CoI: Ms. Katie Hollyhead Liverpool John Moores University N CoI: Dr. Vera Kozhurina-Platais Space Telescope Science Institute Y CoI: Dr. Carmela Lardo Liverpool John Moores University N CoI: Dr. Soeren S. Larsen Radboud Universiteit Nijmegen N CoI: Dr. Alessio Mucciarelli Universita di Bologna N CoI: Florian Niederhofer Leibniz-Institut fur Astrophysik Potsdam N (AIP) CoI: Dr. Maurizio Salaris Liverpool John Moores University N CoI: Dr. Christopher Usher Liverpool John Moores University N ------------------------------------------------------------------------------------ Abstract 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. ------------------------------------------------------------------------------------ Observations Description ------------------------ 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 15061( 5) - 25-Jul-2017 17:48:41 - [ 2] 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 ------------------------------------------------------------------------------------ 15061( 5) - 25-Jul-2017 17:48:41 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC419 STELLAR CLUSTER, RA=01H08M17.0059S +/- 0.1", J2000 V = 10.5 GLOBULAR CLUSTER, OPEN DEC=-72D53'16.59" +/- 0.1" CLUSTER Reference Frame: Other: SIMBAD Extended: NO Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC104 STELLAR CLUSTER, RA=00H24M15.2600S +/- 0.1", J2000 V = 12 GLOBULAR CLUSTER DEC=-72D05'47.93" +/- 0.1" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 15061( 5) - 25-Jul-2017 17:48:41 - [ 4] Visit: 01 (Visit 01 - NGC 419) Visit Requirements: SCHED 70%; ORIENT 306D TO 308 D 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 NGC419 WFC3/UVI ACCUM UVIS1 F343N FLASH=8 1 3244 S POS TARG 0 , 0 S see below (2924.3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC419 WFC3/UVI ACCUM UVIS1 F343N CR-SPLIT=2, FLASH=10 1 3355 S POS TARG 0.18, 2.44 S see below (2901 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC419 WFC3/UVI ACCUM UVIS1 F343N CR-SPLIT=2, FLASH=10 1 3355 S POS TARG -0.18, -2.44 S see below (2901 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC419 WFC3/UVI ACCUM UVIS1 F343N FLASH=8 1 3355 S POS TARG -0.18, 2.44 S see below (3035.5 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC419 WFC3/UVI ACCUM UVIS1 F343N FLASH=6 1 3355 S POS TARG 0.18, -2.44 S see below (3036 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC419 1 WFC3/UVI ACCUM UVIS1 F343N none none none none 1 2924.3 S S NGC419 2 WFC3/UVI ACCUM UVIS1 F343N none none none 1 2 1450.5 S S NGC419 2 WFC3/UVI ACCUM UVIS1 F343N none none none 2 2 1450.5 S S NGC419 3 WFC3/UVI ACCUM UVIS1 F343N none none none 1 3 1450.5 S S NGC419 3 WFC3/UVI ACCUM UVIS1 F343N none none none 2 3 1450.5 S S NGC419 4 WFC3/UVI ACCUM UVIS1 F343N none none none none 4 3035.5 S S NGC419 5 WFC3/UVI ACCUM UVIS1 F343N none none none none 5 3036.0 S S 15061( 5) - 25-Jul-2017 17:48:41 - [ 5] Visit: 02 (Visit 02 - NGC 419) Visit Requirements: SCHED 70%; ORIENT 306D TO 308 D 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 NGC419 WFC3/UVI ACCUM UVIS1 F336W FLASH=8, CR-SPLIT=2 1 3000 S POS TARG 0 , 0 S see below (2790 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC419 WFC3/UVI ACCUM UVIS1 F336W FLASH=4 1 3000 S POS TARG 0.18, 2.44 S see below (3036 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC419 WFC3/UVI ACCUM UVIS1 F438W CR-SPLIT=2 1 3000 S POS TARG 0 , 0 S see below (2908 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC419 1 WFC3/UVI ACCUM UVIS1 F336W none none none 1 1 1395.0 S S NGC419 1 WFC3/UVI ACCUM UVIS1 F336W none none none 2 1 1395.0 S S NGC419 2 WFC3/UVI ACCUM UVIS1 F336W none none none none 2 3036.0 S S NGC419 3 WFC3/UVI ACCUM UVIS1 F438W none none none 1 3 1454.0 S S NGC419 3 WFC3/UVI ACCUM UVIS1 F438W none none none 2 3 1454.0 S S 15061( 5) - 25-Jul-2017 17:48:41 - [ 6] Visit: 03 (Visit 03 - NGC104) Visit Requirements: SCHED 30%; ORIENT 180D TO 180 D 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 NGC104 WFC3/UVI ACCUM UVIS F438W FLASH=12 1 65 S POS TARG 0, 0; GS ACQ S see below SCENARIO BASE1B3 (40 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC104 WFC3/UVI ACCUM UVIS F438W FLASH=8 1 460 S POS TARG 0.18, 2.44 S see below (435 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC104 WFC3/UVI ACCUM UVIS F438W FLASH=12 1 155 S POS TARG -0.18, -2.44 S see below (130 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC104 WFC3/UVI ACCUM UVIS F343N FLASH=10 1 1325 S POS TARG 0, 0 S (1325 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC104 WFC3/UVI ACCUM UVIS F343N FLASH=10 1 730 S (730 POS TARG -0.18, 2.44 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC104 1 WFC3/UVI ACCUM UVIS F438W none none none none 1 40.0 S S NGC104 2 WFC3/UVI ACCUM UVIS F438W none none none none 1 435.0 S S NGC104 3 WFC3/UVI ACCUM UVIS F438W none none none none 1 130.0 S S NGC104 4 WFC3/UVI ACCUM UVIS F343N none none none none 1 N/A S NGC104 5 WFC3/UVI ACCUM UVIS F343N none none none none 1 N/A S 15061( 5) - 25-Jul-2017 17:48:41 - [ 7] Summary Form for Proposal 15061 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS, UVIS1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2, FLASH=10, FLASH=12, FLASH=4, FLASH=6, FLASH=8 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO BASE1B3, ORIENT 180D TO 180 D, ORIENT 306D TO 308 D, POS TARG -0.18, -2.44, POS TARG -0.18, 2.44, POS TARG 0 , 0, POS TARG 0, 0, POS TARG 0.18, -2.44, POS TARG 0.18, 2.44, SCHED 30%, SCHED 70% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W, F343N, F438W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC104, NGC419 ------------------------------------------------------------------------------------------------------------------------------------