13746( 4) - 26-Aug-2014 14:05:28 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13746 Version: 4 Check-in Time: 26-Aug-2014 14:05:28 STScI Edit Number: 0 Title Is the Crater satellite the Milky Way's Smallest Dwarf Galaxy or its Largest Globular Cluster? ------------------------------------------------------------------------------------ Type Cycle GO 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Matthew G. Walker Carnegie Mellon University Y CoI: Dr. Vasily Belokurov University of Cambridge N CoI: Dr. Sergey Koposov University of Cambridge N CoI: Dr. Edward W. Olszewski University of Arizona N CoI: Dr. Mario L. Mateo University of Michigan N CoI: Dr. Daniel R. Weisz University of Washington N CoI: Prof. Mark Gieles University of Surrey N CoI: Filippo Contenta University of Surrey N ------------------------------------------------------------------------------------ Abstract We propose deep ACS/WFC3 photometry that will reveal the nature and origin of the Galactic satellite known as 'Crater'. Crater exhibits properties intermediate between dwarf galaxies and globular clusters. As a dwarf galaxy, Crater would be the smallest and least massive known in the Galactic halo. As a globular cluster, Crater would be the largest and most distant. Our photometric observations will tell the age, metallicity, limits on metallicity spread, mass function and dynamical state of Crater's stellar population(s). We will use this information to distinguish whether Crater is 1) a dwarf galaxy that formed in a dark matter potential, or 2) a globular cluster that has grown to its current size via internal dynamical evolution. In either case, we will learn what mechanisms are responsible for Crater's extreme properties. ------------------------------------------------------------------------------------ Observations Description ------------------------ This proposal is to obtain deep imaging in two filters, and imaging to ~V=24.5 in two filters for the newly discovered Crater globular cluster. A minor modification was made to the published central coordinates to help to avoid the two very bright field stars. In addition, small pos-targs refined the position, a different POS-TARG for the WFC3 field snd for the ACS field. The primary goal of visit 1, one orbit, is to get deep imaging with WFC3 in F390M. There are ORIENT constraints to avoid the two bright stars(the WFC3 FOV is smaller than the ACS below). The primary goal of visit 2, 4 orbits, is to get deep imaging with ACS in F606 and F814. We also obtain short exposures in F555 and F814 and F606. There is a small 13746( 4) - 26-Aug-2014 14:05:28 - [ 2] pos-targ difference in exposure 3 of visit 2 so that the two short F555W exposures have dithers between them. The F555 data is to match the F390 WFC3 data, and allows us to use a previous calibration to obtain metallicities of stars in this object. We apply some ORIENTS to avoid the two bright stars. the ORIENTS are a bit stringent in order to ensure that we avoid bright stars AND get all of Crater at all orients. ------------------------------------------------------------------------------------ 13746( 4) - 26-Aug-2014 14:05:28 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CRATER STELLAR CLUSTER, RA=11H36M16.5150S, J2000 V = 20 GLOBULAR CLUSTER DEC=-10D52'0.87" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 2 CRATER-POS2 STELLAR CLUSTER, RA=11H36M16.4549S, J2000 V = 20 GLOBULAR CLUSTER DEC=-10D51'37.09" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 13746( 4) - 26-Aug-2014 14:05:28 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 3.011 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.28 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 13746( 4) - 26-Aug-2014 14:05:28 - [ 5] Visit: 01 Visit Requirements: SCHED 100%; ORIENT 0D TO 4 D; ORIENT 47D TO 96 D; ORIENT 129D TO 184 D; ORIENT 225D TO 279 D; ORIENT 317D TO 359.9 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 CRATER WFC3/UVI ACCUM UVIS-CENT F390M FLASH=8 1 150 S (150 POS TARG -1.16, -1.63 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 2 CRATER WFC3/UVI ACCUM UVIS-CENT F390M FLASH=7 1 700 S POS TARG -1.16, -1.63; S ER (2100 S) PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ CRATER 1 WFC3/UVI ACCUM UVIS-CEN F390M none none none none 1 N/A S TER CRATER 2 WFC3/UVI ACCUM UVIS-CEN F390M 1 none none none 1 N/A S TER CRATER 2 WFC3/UVI ACCUM UVIS-CEN F390M 2 none none none 1 N/A S TER CRATER 2 WFC3/UVI ACCUM UVIS-CEN F390M 3 none none none 1 N/A S TER 13746( 4) - 26-Aug-2014 14:05:28 - [ 6] Visit: 02 Visit Requirements: SCHED 100%; ORIENT 0D TO 37 D; ORIENT 86D TO 123 D; ORIENT 172D TO 217 D; ORIENT 265D TO 303 D; ORIENT 351D TO 359.9 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 CRATER-POS2 ACS/WFC ACCUM WFCENTER F555W 1 120 S (120 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 CRATER-POS2 ACS/WFC ACCUM WFCENTER F606W 1 600 S PATTERN 2 2 (1800 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 CRATER-POS2 ACS/WFC ACCUM WFCENTER F555W 1 120 S (120 POS TARG 0.25, 0.35 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 CRATER-POS2 ACS/WFC ACCUM WFCENTER F814W 1 650 S PATTERN 2 4 (1950 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 CRATER-POS2 ACS/WFC ACCUM WFCENTER F814W 1 150 S (150 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 CRATER-POS2 ACS/WFC ACCUM WFCENTER F814W 1 665 S PATTERN 2 6 (1995 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 CRATER-POS2 ACS/WFC ACCUM WFCENTER F606W 1 150 S (150 S) ------------------------------------------------------------------------------------------------------------------------------------ 8 CRATER-POS2 ACS/WFC ACCUM WFCENTER F606W 1 655 S PATTERN 2 8 (1965 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 | ------------------------------------------------------------------------------------------------------------------------------------ CRATER-POS2 1 ACS/WFC ACCUM WFCENTER F555W none none none none 1 N/A CRATER-POS2 2 ACS/WFC ACCUM WFCENTER F606W 1 none none none 1 N/A CRATER-POS2 2 ACS/WFC ACCUM WFCENTER F606W 2 none none none 1 N/A CRATER-POS2 2 ACS/WFC ACCUM WFCENTER F606W 3 none none none 1 N/A CRATER-POS2 3 ACS/WFC ACCUM WFCENTER F555W none none none none 2 N/A CRATER-POS2 4 ACS/WFC ACCUM WFCENTER F814W 1 none none none 2 N/A CRATER-POS2 4 ACS/WFC ACCUM WFCENTER F814W 2 none none none 2 N/A CRATER-POS2 4 ACS/WFC ACCUM WFCENTER F814W 3 none none none 2 N/A CRATER-POS2 5 ACS/WFC ACCUM WFCENTER F814W none none none none 3 N/A CRATER-POS2 6 ACS/WFC ACCUM WFCENTER F814W 1 none none none 3 N/A CRATER-POS2 6 ACS/WFC ACCUM WFCENTER F814W 2 none none none 3 N/A 13746( 4) - 26-Aug-2014 14:05:28 - [ 7] 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 | ------------------------------------------------------------------------------------------------------------------------------------ CRATER-POS2 6 ACS/WFC ACCUM WFCENTER F814W 3 none none none 3 N/A CRATER-POS2 7 ACS/WFC ACCUM WFCENTER F606W none none none none 4 N/A CRATER-POS2 8 ACS/WFC ACCUM WFCENTER F606W 1 none none none 4 N/A CRATER-POS2 8 ACS/WFC ACCUM WFCENTER F606W 2 none none none 4 N/A CRATER-POS2 8 ACS/WFC ACCUM WFCENTER F606W 3 none none none 4 N/A 13746( 4) - 26-Aug-2014 14:05:28 - [ 8] Summary Form for Proposal 13746 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER, WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=7, FLASH=8 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 0D TO 37 D, ORIENT 0D TO 4 D, ORIENT 129D TO 184 D, ORIENT 172D TO 217 D, ORIENT 225D TO 279 D, ORIENT 265D TO 303 D, ORIENT 317D TO 359.9 D, ORIENT 351D TO 359.9 D, ORIENT 47D TO 96 D, ORIENT 86D TO 123 D, PATTERN 1 2, PATTERN 2 2, PATTERN 2 4, PATTERN 2 6, PATTERN 2 8, POS TARG -1.16, -1.63, POS TARG 0.25, 0.35, SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F390M, F555W, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names CRATER, CRATER-POS2 ------------------------------------------------------------------------------------------------------------------------------------