15078( 2) - 19-Jul-2017 14:48:25 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15078 Version: 2 Check-in Time: 19-Jul-2017 14:48:25 STScI Edit Number: 0 Title Initial conditions of multiple populations in the dynamically most pristine globular cluster, NGC 2419 ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Soeren S. Larsen Radboud Universiteit Nijmegen Y CoI: Dr. Nate Bastian Liverpool John Moores University N CoI: Dr. Holger Baumgardt University of Queensland N CoI: Prof. Jean P. Brodie University of California - Santa Cruz N CoI: SVEA S HERNANDEZ Radboud Universiteit Nijmegen N ------------------------------------------------------------------------------------ Abstract The remote globular cluster (GC) NGC 2419 is unique in the Milky Way by having a half-mass relaxation time that exceeds the age of the Universe. This makes it an ideal target for studying the initial spatial distributions of sub-populations within the cluster. Most scenarios for the origin of multiple populations in GCs predict that enriched ("2nd-generation") stars should have a more centrally concentrated radial distribution than the pristine stars. This has indeed been found by a number of studies for the outer regions of GCs, although these (mostly ground-based) studies generally did not probe the center. We have recently found the opposite trend from HST observations of the central regions of the GC M15, where the enriched stars are the least centrally concentrated. This suggests a more complex situation than implied by most formation scenarios. Here we propose to determine the radial distributions of subpopulations in the central regions of NGC 2419 and determine whether it formed with a more centrally concentrated pristine population. This unique, dynamically pristine environment is free of the dynamical effects (such as orbital mixing and mass segregation) that may have modified the spatial distributions in other clusters, and will thus directly reflect the initial conditions. We will use F336W and F343N data to unambiguously separate pristine and enriched stars, based on their N abundances (that are enhanced by about 2 dex in enriched stars). By combining these data with archival observations at longer wavelengths, we will also determine the He abundances of the different populations. ------------------------------------------------------------------------------------ Observations Description ------------------------ Images of NGC 2419 will be obtained with WFC3-UVIS in F343N (6 orbits) and F336W (3 orbits). The exposures will be grouped into visits of three orbits each, with two such visits for F343N and one visit for F336W. In each visit, the exposures will be dithered according to the 3x2 "C6" dither pattern in ISR WFC3-2010-09, i.e., a 3 point line dither (one dither point per orbit) with 2 point sub-dithers. ------------------------------------------------------------------------------------ 15078( 2) - 19-Jul-2017 14:48:25 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-2419 STELLAR CLUSTER, RA=07H38M8.5100S, J2000 V = 10.05 GLOBULAR CLUSTER DEC=+38D52'54.90" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 15078( 2) - 19-Jul-2017 14:48:25 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-MOS-DITH-LINE WFC3-UVIS-MOS-DITH-LINE Pattern_Purpose DITHER DITHER Number_Of_Points 3 2 Point_Spacing 0.135 0.109 Line_Spacing Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 46.84 25.07 Angle_Between_Sides Center_Pattern YES NO ------------------------------------------------------------------------------------------------------------------------------------ 15078( 2) - 19-Jul-2017 14:48:25 - [ 4] Visit: 01 (NGC2419-F343N) 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 NGC-2419 WFC3/UVI ACCUM UVIS F343N FLASH=10 1 1400 S PATTERN 1 1 S see below (8576 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 1 1 none none 1 1392.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 1 2 none none 1 1392.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 2 1 none none 2 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 2 2 none none 2 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 3 1 none none 3 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 3 2 none none 3 1448.0 S S 15078( 2) - 19-Jul-2017 14:48:25 - [ 5] Visit: 02 (NGC2419-F343N) Visit Requirements: SAME ORIENT AS 01 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 NGC-2419 WFC3/UVI ACCUM UVIS F343N FLASH=10 1 1400 S PATTERN 1 1 S see below (8576 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 1 1 none none 1 1392.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 1 2 none none 1 1392.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 2 1 none none 2 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 2 2 none none 2 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 3 1 none none 3 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F343N 3 2 none none 3 1448.0 S S 15078( 2) - 19-Jul-2017 14:48:25 - [ 6] Visit: 03 (NGC2419-F336W) Visit Requirements: SAME ORIENT AS 01 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 NGC-2419 WFC3/UVI ACCUM UVIS F336W FLASH=10 1 1400 S PATTERN 1 1 S see below (8576 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-2419 1 WFC3/UVI ACCUM UVIS F336W 1 1 none none 1 1392.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F336W 1 2 none none 1 1392.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F336W 2 1 none none 2 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F336W 2 2 none none 2 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F336W 3 1 none none 3 1448.0 S S NGC-2419 1 WFC3/UVI ACCUM UVIS F336W 3 2 none none 3 1448.0 S S 15078( 2) - 19-Jul-2017 14:48:25 - [ 7] Summary Form for Proposal 15078 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=10 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W, F343N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC-2419 ------------------------------------------------------------------------------------------------------------------------------------