11297( 4) - 05/16/07 13:21 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11297 Version: 4 Check-in Time: 16-May-2007 17:20:59 STScI Edit Number: 2 Title Reducing Systematic Errors on the Hubble Constant: Metallicity Calibration of the Cepheid PL Relation ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Wendy L. Freedman Carnegie Institution of Washington CoI: Dr. Barry F. Madore Carnegie Institution of Washington N ------------------------------------------------------------------------------------ Abstract Reducing the systematic errors on the Hubble constant is still of significance and of immediate importance to modern cosmology. One of the largest remaining uncertainties in the Cepheid-based distance scale (which itself is at the foundation of the HST Key Project determination of H_o) which can now be addressed directly by HST, is the effect of metallicity on the Cepheid Period-Luminosity relation. Three chemically distinct regions in M101 will be used to directly measure and thereby calibrate the change in zero point of the Cepheid PL relation over a range of metallicities that run from SMC-like, through Solar, to metallicities as high as the most metal-enriched galaxies in the pure Hubble flow. ACS for the first time offers the opportunity to make a precise calibration of this effect which currently accounts for at least a third of the total systematic uncertainty on Ho. The calibration will be made in the V and I bandpasses so as to be immediately and directly applicable to the entire HST Cepheid-based distance scale sample, and most especially to the highest-metallicity galaxies that were hosts to the Type Ia supernovae, which were then used to extend the the distance scale calibration out to cosmologically significant distances. ------------------------------------------------------------------------------------ 11297( 4) - 05/16/07 13:21 - [ 2] Observations Description ------------------------ Three fields in M101 will be monitored in the V and I bandpasses searching for Cepheids. A window of 45 days will be optimally sampled by 12 observations. A single orbit containing both the V and the I exposures will reach the required signal-to-noise ratio for the shortest-period (3-5 day) Cepheids Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11297( 4) - 05/16/07 13:21 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-F1 GALAXY, SPIRAL ARM, RA=14H03M28.8000S +/- 0.1", J2000 V = 23.0+/-2.0 SPIRAL, STAR FORMING DEC=+54D21'35.00" +/- 0.1" REGION Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the NED database. changed to IRCS coordinate frame since GSC2 is not recognized. 2 M101-F2 GALAXY, SPIRAL ARM, RA=14H02M51.0000S +/- 0.1", J2000 V = 23.0+/-2.0 STAR FORMING REGION, DEC=+54D20'22.00" +/- 0.1" SPIRAL Reference Frame: ICRS Comments: changed to IRCS coordinate frame since GSC2 is not recognized. 3 M101-F3 GALAXY, STAR FORMING RA=14H02M28.0000S +/- 0.1", J2000 V = 23.0+/-2.0 REGION, SPIRAL ARM, DEC=+54D18'20.00" +/- 0.1" SPIRAL Reference Frame: ICRS Comments: These coordinates have been changed from 14 02 29.0, +54 18 20, to acquire guide star coverage. 11297( 4) - 05/16/07 13:21 - [ 4] Visit: 62 Visit Priority: Visit Requirements: ORIENT 245.0D TO 245.0 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 M101-F3 WFPC2 IMAGE WFALL F814W 1 350 S GS ACQ SCENARIO SINGLE Comments: there are np time constraints on this visit ------------------------------------------------------------------------------------------------------------------------------------ 2 M101-F3 WFPC2 IMAGE WFALL F814W 1 350 S ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-F3 WFPC2 IMAGE WFALL F555W 1 500 S ------------------------------------------------------------------------------------------------------------------------------------ 4 M101-F3 WFPC2 IMAGE WFALL F555W 1 500 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-F3 1 WFPC2 IMAGE WFALL F814W none none none none 1 N/A M101-F3 2 WFPC2 IMAGE WFALL F814W none none none none 1 N/A M101-F3 3 WFPC2 IMAGE WFALL F555W none none none none 1 N/A M101-F3 4 WFPC2 IMAGE WFALL F555W none none none none 1 N/A 11297( 4) - 05/16/07 13:21 - [ 5] Visit: 63 Visit Priority: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-F2 WFPC2 IMAGE WFALL F814W 1 350 S ------------------------------------------------------------------------------------------------------------------------------------ 2 M101-F2 WFPC2 IMAGE WFALL F814W 1 350 S ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-F2 WFPC2 IMAGE WFALL F555W 1 500 S ------------------------------------------------------------------------------------------------------------------------------------ 4 M101-F2 WFPC2 IMAGE WFALL F555W 1 500 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-F2 1 WFPC2 IMAGE WFALL F814W none none none none 1 N/A M101-F2 2 WFPC2 IMAGE WFALL F814W none none none none 1 N/A M101-F2 3 WFPC2 IMAGE WFALL F555W none none none none 1 N/A M101-F2 4 WFPC2 IMAGE WFALL F555W none none none none 1 N/A 11297( 4) - 05/16/07 13:21 - [ 6] Visit: 64 Visit Priority: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-F1 WFPC2 IMAGE WFALL F814W 1 350 S ------------------------------------------------------------------------------------------------------------------------------------ 2 M101-F1 WFPC2 IMAGE WFALL F814W 1 350 S ------------------------------------------------------------------------------------------------------------------------------------ 3 M101-F1 WFPC2 IMAGE WFALL F555W 1 500 S ------------------------------------------------------------------------------------------------------------------------------------ 4 M101-F1 WFPC2 IMAGE WFALL F555W 1 500 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 | ------------------------------------------------------------------------------------------------------------------------------------ M101-F1 1 WFPC2 IMAGE WFALL F814W none none none none 1 N/A M101-F1 2 WFPC2 IMAGE WFALL F814W none none none none 1 N/A M101-F1 3 WFPC2 IMAGE WFALL F555W none none none none 1 N/A M101-F1 4 WFPC2 IMAGE WFALL F555W none none none none 1 N/A 11297( 4) - 05/16/07 13:21 - [ 7] Summary Form for Proposal 11297 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFALL ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 245.0D TO 245.0 D; GS ACQ SCENARIO SINGLE; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names M101-F3 M101-F2 M101-F1 ------------------------------------------------------------------------------------------------------------------------------------