9720( 9) - 06/24/03 06:35 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9720 Version: 9 Check-in Date: 24-Jun-2003 06:33:53 1.Proposal Title: Age-dating Star Clusters in M101 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 12 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Dr. Rupali Chandar Space Telescope Science Institute CoI: Dr. Brad C. Whitmore Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract M101 represents perhaps our best chance to study the stellar population of a luminous, late type spiral galaxy, due to both its proximity and its face-on orientation. For these reasons, 13 orbits of HST ACS observing time were allocated in Cycle 11 to obtain a 4x4 mosaic image of M101 in BVI . Unfortunately, a degeneracy between age and reddening exists when only these three bands are available. Hence, we propose to augment these observations by obtaining WFPC2 U band and ACS H alpha images. This will enable the accurate determination of ages for the young clusters, secure identifications of 75-100 old globular clusters, and allow a quantitative study of the HII region sizes and structures. Some of the specific questions we will address are: How do the young clusters form and evolve? What fraction of the clusters dissolve and on what timescales? Do clusters evolve with a continuum of properties? Using WFPC2 and ACS in parallel, and making use of the fact that M101 is in the CVZ, allows us to greatly enhance the science return of previous HST observations for the cost of only 4 orbits. ------------------------------------------------------------------------------------ 9720( 9) - 06/24/03 06:35 - [ 2] Observations Description ------------------------ We are using WFPC2 as the primary instrument (for U band imaging of M101), with ACS WFC used in coordinated parallel for Halpha observations. The WFPC2 and ACS fields are offset from each other by about 300 arcseconds. The most effective way to cover the same fields with both U and Halpha filters is to observe the two fields 6 months apart, so that the orientation ofthe fields flips 180 degrees, and the ACS falls on the previous WFPC2 field of view, and vice versa. We have carefully chosen our field pointings to overlap regions with previous ACS WFC (BVI) imaging from GO-9490, and to cover different environments in M101 including the nucleus, spiral arms, and inter-arm regions. The main constraints for this program come from orientation restrictions, which allow us to target the most interesting fields. For schedulability, we can tolerate an orientation angle which is plus or minus 5 degrees from our most desirable orientation. These have been selected for visits 1 and 3. Once these observations have occurred, than the orientation angles required in visits and 2 and 4 are linked to visits 1 and 3 respectively, such that they occur at an orientation which differs by 180 degrees, with a plus or minus 2 degree tolerance. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9720( 9) - 06/24/03 06:35 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-POS1 GALAXY, SPIRAL RA=14H03M7.86S +/- 0.5", J2000 V = 15.0 DEC=+54D21'3.73" +/- 0.5", PLATE-ID=003A Coordinate Source: GUIDE_STAR_CATALOG 2 M101-POS2 GALAXY, SPIRAL RA=14H03M44.68S +/- 0.5", J2000 V = 15.0 DEC=+54D19'16.99" +/- 0.5", PLATE-ID=003A Coordinate Source: GUIDE_STAR_CATALOG 3 M101-POS3 GALAXY, SPIRAL RA=14H03M13.0S +/- 0.5", J2000 V = 15.0 DEC=+54D19'14.51" +/- 0.5", PLATE-ID=003A Coordinate Source: GUIDE_STAR_CATALOG 4 M101-POS4 GALAXY, SPIRAL RA=14H03M21.5S +/- 0.5", J2000 V = 15.0 DEC=+54D24'40.37" +/- 0.5", PLATE-ID=003A Coordinate Source: GUIDE_STAR_CATALOG 9720( 9) - 06/24/03 06:35 - [ 4] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE SCHED 30% ORIENT 235.0D TO 245.0 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-POS1 WFPC2 IMAGE WFALL-F F336W CR-SPLIT=DEF 1 2550 S PAR 2 WITH 1 IX ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY ACS/WF ACCUM WFC F658N CR-SPLIT=2 1 2440 S C ------------------------------------------------------------------------------------------------------------------------------------ 9720( 9) - 06/24/03 06:35 - [ 5] Visit: 02 Visit Priority: Visit Requirements: PCS MODE FINE SCHED 30% ORIENT 178.0D TO -178.0D FROM 01 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-POS2 WFPC2 IMAGE WFALL-F F336W CR-SPLIT=DEF 1 2550 S PAR 2 WITH 1 GS ACQ IX SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY ACS/WF ACCUM WFC F658N CR-SPLIT=2 1 2430 S C ------------------------------------------------------------------------------------------------------------------------------------ 9720( 9) - 06/24/03 06:35 - [ 6] Visit: 03 Visit Priority: Visit Requirements: ORIENT 140.0D TO 150.0 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-POS3 WFPC2 IMAGE WFALL-F F336W CR-SPLIT=DEF 1 2550 S PAR 2 WITH 1 IX ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY ACS/WF ACCUM WFC F658N CR-SPLIT=2 1 2430 S C ------------------------------------------------------------------------------------------------------------------------------------ 9720( 9) - 06/24/03 06:35 - [ 7] Visit: 04 Visit Priority: Visit Requirements: ORIENT 178.0D TO -178.0D FROM 03 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M101-POS4 WFPC2 IMAGE WFALL-F F336W CR-SPLIT=DEF 1 2550 S PAR 2 WITH 1 GS ACQ IX SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY ACS/WF ACCUM WFC F658N CR-SPLIT=2 1 2430 S C ------------------------------------------------------------------------------------------------------------------------------------ 9720( 9) - 06/24/03 06:35 - [ 8] Summary Form for Proposal 9720 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFALL-FIX WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=DEF CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE SCHED 30% ORIENT 235.0D TO 245.0 D PAR 2 WITH 1 PCS MODE FINE SCHED 30% ORIENT 178.0D TO -178.0D FROM 01 PAR 2 WITH 1 GS ACQ SCENARIO SINGLE ORIENT 140.0D TO 150.0 D ORIENT 178.0D TO -178.0D FROM 03 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W F658N ------------------------------------------------------------------------------------------------------------------------------------ Target Names M101-POS1 ANY M101-POS2 M101-POS3 M101-POS4 ------------------------------------------------------------------------------------------------------------------------------------