11141( 2) - 05/09/07 13:04 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11141 Version: 2 Check-in Time: 09-May-2007 17:03:54 STScI Edit Number: 0 Title White dwarfs in the open star cluster NGC 188 ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Kurtis A. Williams University of Texas at Austin CoI: Dr. Theodore von Hippel University of Texas at Austin N CoI: Dr. James Liebert University of Arizona N CoI: Dr. Michael Bolte University of California - Santa Cruz N CoI: Dr. Michael Montgomery University of Texas at Austin N CoI: Ms. Elizabeth Jeffery University of Texas at Austin N CoI: Dr. Donald E. Winget University of Texas at Austin N ------------------------------------------------------------------------------------ Abstract White dwarf cooling sequences represent the only ways in which we can determine ages of Galactic components such as the disk and the halo, and they are an independent check on main sequence ages of globular star clusters. These age measurements rely heavily on theoretical cooling models, many of which disagree by as much as a few gigayears for the coolest white dwarfs. Further, observations of the white dwarf sequence in the super metal-rich open cluster NGC 6791 have found a white dwarf age several gigayears younger than the accepted cluster age determined by main-sequence fitting. The white dwarf sequence of the solar-metallicity, 7-Gyr old open cluster NGC 188 can provide some much-needed insight into these uncertainties, but previous HST observations were too shallow to detect the oldest, faintest white dwarfs in the cluster. We propose deep imaging of two fields at the center of the cluster with the following goals: (1) To detect the end of the white dwarf cooling sequence, providing a much-needed empirical data point for cool white dwarf evolutionary models, (2) to compare the white dwarf luminosity function of NGC 188 with that of NGC 6791 to determine if the odd white dwarf sequence in the latter cluster is due to the cluster's high metallicity or due to a shortcoming in theoretical models, and (3) to determine via photometry the masses of white dwarfs formed by solar-mass stars, a quantity not yet empirically measured. ------------------------------------------------------------------------------------ 11141( 2) - 05/09/07 13:04 - [ 2] Observations Description ------------------------ Our observations represent a second epoch of imaging of two fields in the open cluster NGC 188 first imaged in GO 7371. The three primary goals of the observations are: (1) In one deep field, obtain V and I photometry with S/N~14 for white dwarfs as faint as V=27.2 (0.2 mag fainter than the faintest expected white dwarfs in this 7 Gyr-old cluster); (2) In a second, shallower field, obtain accurate V and I photometry for white dwarfs as faint as V=26.5 for comparison with the anomalous white dwarf luminosity function of the open cluster NGC 6791; and (3) To obtain measurements of proper motions of white dwarfs imaged in both fields in both epochs. In order to maximize the overlap of these observations with the first epoch imaging and in order to minimize the impact of distortions on proper motion measurements, we constrain the ORIENT of each field to within 10 degrees of the first epoch orientation; multiple visits to each field are constrained to be at the same ORIENT as the first visit. As several exposures will be taken in each filter at each field, we have set CR- SPLIT=NO. Both BOX and LINE dither patterns were selected for the purposes of sub-sampling the WF PSF and to aid in cosmic ray and hot pixel rejection. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11141( 2) - 05/09/07 13:04 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-2 STELLAR CLUSTER, OPEN RA=00H47M57.0000S +/- 0.1", J2000 V = 27.25+/-0.07 CLUSTER DEC=+85D15'52.00" +/- 0.1" Reference Frame: ICRS Comments: The V-magnitude indicate the faintest objects we wish to detect in this field. 3 NGC188-3 STELLAR CLUSTER, OPEN RA=00H45M56.5000S +/- 0.1", J2000 V = 26.5+/-0.07 CLUSTER DEC=+85D15'53.00" +/- 0.1" Reference Frame: ICRS Comments: The V-magnitude indicate the faintest objects we wish to detect in this field. 11141( 2) - 05/09/07 13:04 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFPC2-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.559017 Line_Spacing 0.559017 Coordinate_Frame POS-TARG Pattern_Orient 26.56505 Angle_Between_Sides 143.130102 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFPC2-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.3535 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 45.0 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 11141( 2) - 05/09/07 13:04 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 180.0D TO 200.0 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-2 WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 2 1200 S PATTERN 1 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC188-2 WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 1 1200 S PATTERN 2 2 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC188-2 1 WFPC2 IMAGE WFALL F814W 1 none 1 none 1 N/A NGC188-2 1 WFPC2 IMAGE WFALL F814W 1 none 2 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 2 none 1 none 2 N/A NGC188-2 1 WFPC2 IMAGE WFALL F814W 2 none 2 none 2 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 3 none 1 none 3 N/A NGC188-2 1 WFPC2 IMAGE WFALL F814W 3 none 2 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 4 none 1 none 4 N/A NGC188-2 1 WFPC2 IMAGE WFALL F814W 4 none 2 none 4 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F814W 1 none none none 5 1200.0 S NGC188-2 2 WFPC2 IMAGE WFALL F814W 2 none none none 5 1300.0 S 11141( 2) - 05/09/07 13:04 - [ 6] Visit: 02 Visit Priority: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-2 WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 2 1200 S PATTERN 1 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC188-2 WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 1 1200 S PATTERN 2 2 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC188-2 1 WFPC2 IMAGE WFALL F814W 1 none 1 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 1 none 2 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 2 none 1 none 2 1200.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 2 none 2 none 2 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 3 none 1 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 3 none 2 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 4 none 1 none 4 1200.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 4 none 2 none 4 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F814W 1 none none none 5 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F814W 2 none none none 5 1300.0 S 11141( 2) - 05/09/07 13:04 - [ 7] Visit: 03 Visit Priority: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-2 WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 2 1200 S PATTERN 1 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC188-2 WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 1 1200 S PATTERN 2 2 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC188-2 1 WFPC2 IMAGE WFALL F814W 1 none 1 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 1 none 2 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 2 none 1 none 2 N/A NGC188-2 1 WFPC2 IMAGE WFALL F814W 2 none 2 none 2 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 3 none 1 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 3 none 2 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 4 none 1 none 4 1200.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 4 none 2 none 4 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F814W 1 none none none 5 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F814W 2 none none none 5 1300.0 S 11141( 2) - 05/09/07 13:04 - [ 8] Visit: 04 Visit Priority: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-2 WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 2 1200 S PATTERN 2 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC188-2 WFPC2 IMAGE WFALL F606W CR-SPLIT=NO 3 1200 S PATTERN 2 2 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC188-2 1 WFPC2 IMAGE WFALL F814W 1 none 1 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 1 none 2 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 2 none 1 none 2 1200.0 S NGC188-2 1 WFPC2 IMAGE WFALL F814W 2 none 2 none 2 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F606W 1 none 1 none 3 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F606W 1 none 2 none 3 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F606W 1 none 3 none 4 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F606W 2 none 1 none 4 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F606W 2 none 2 none 5 1300.0 S NGC188-2 2 WFPC2 IMAGE WFALL F606W 2 none 3 none 5 1300.0 S 11141( 2) - 05/09/07 13:04 - [ 9] Visit: 05 Visit Priority: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-2 WFPC2 IMAGE WFALL F606W CR-SPLIT=NO 2 1200 S PATTERN 1 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC188-2 1 WFPC2 IMAGE WFALL F606W 1 none 1 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 1 none 2 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 2 none 1 none 2 N/A NGC188-2 1 WFPC2 IMAGE WFALL F606W 2 none 2 none 2 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 3 none 1 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 3 none 2 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 4 none 1 none 4 N/A NGC188-2 1 WFPC2 IMAGE WFALL F606W 4 none 2 none 4 1300.0 S 11141( 2) - 05/09/07 13:04 - [ 10] Visit: 06 Visit Priority: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-2 WFPC2 IMAGE WFALL F606W CR-SPLIT=NO 2 1200 S PATTERN 1 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC188-2 1 WFPC2 IMAGE WFALL F606W 1 none 1 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 1 none 2 none 1 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 2 none 1 none 2 N/A NGC188-2 1 WFPC2 IMAGE WFALL F606W 2 none 2 none 2 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 3 none 1 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 3 none 2 none 3 1300.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 4 none 1 none 4 1200.0 S NGC188-2 1 WFPC2 IMAGE WFALL F606W 4 none 2 none 4 1300.0 S 11141( 2) - 05/09/07 13:04 - [ 11] Visit: 07 Visit Priority: Visit Requirements: ORIENT 186.0D TO 206.0 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-3 WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 2 1200 S PATTERN 1 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC188-3 1 WFPC2 IMAGE WFALL F814W 1 none 1 none 1 1300.0 S NGC188-3 1 WFPC2 IMAGE WFALL F814W 1 none 2 none 1 1300.0 S NGC188-3 1 WFPC2 IMAGE WFALL F814W 2 none 1 none 2 N/A NGC188-3 1 WFPC2 IMAGE WFALL F814W 2 none 2 none 2 1300.0 S NGC188-3 1 WFPC2 IMAGE WFALL F814W 3 none 1 none 3 1300.0 S NGC188-3 1 WFPC2 IMAGE WFALL F814W 3 none 2 none 3 1300.0 S NGC188-3 1 WFPC2 IMAGE WFALL F814W 4 none 1 none 4 N/A NGC188-3 1 WFPC2 IMAGE WFALL F814W 4 none 2 none 4 1300.0 S 11141( 2) - 05/09/07 13:04 - [ 12] Visit: 08 Visit Priority: Visit Requirements: SAME ORIENT AS 07 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC188-3 WFPC2 IMAGE WFALL F606W CR-SPLIT=NO 1 1200 S PATTERN 1 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC188-3 WFPC2 IMAGE WFALL F606W CR-SPLIT=NO 1 1200 S PATTERN 2 2 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC188-3 1 WFPC2 IMAGE WFALL F606W 1 none none none 1 1300.0 S NGC188-3 1 WFPC2 IMAGE WFALL F606W 2 none none none 1 1300.0 S NGC188-3 1 WFPC2 IMAGE WFALL F606W 3 none none none 2 1200.0 S NGC188-3 1 WFPC2 IMAGE WFALL F606W 4 none none none 2 1300.0 S NGC188-3 2 WFPC2 IMAGE WFALL F606W 1 none none none 3 1300.0 S NGC188-3 2 WFPC2 IMAGE WFALL F606W 2 none none none 3 1300.0 S 11141( 2) - 05/09/07 13:04 - [ 13] Summary Form for Proposal 11141 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFALL ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 180.0D TO 200.0 D; PATTERN 1 1; PATTERN 2 2; SAME ORIENT AS 01; PATTERN 2 1; ORIENT 186.0D TO 206.0 D; SAME ORIENT AS 07; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC188-2 NGC188-3 ------------------------------------------------------------------------------------------------------------------------------------