10604( 3) - 05/11/05 09:06 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10604 Version: 3 Check-in Date: 11-May-2005 13:05:39 1.Proposal Title: The Formation History of the M81 Spheroid ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance GO 14 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Ata Sarajedini University of Florida CoI: Dr. Rupali Chandar Space Telescope Science Institute Y CoI: Dr. Patrick R. Durrell Youngstown State University N ------------------------------------------------------------------------------------ 6. Abstract Spheroidal stellar populations (elliptical galaxies, bulges, and halos) contain a significant fraction of all stars and metals in the local universe. The mechanisms responsible for their formation are ultimately the ones which governed galaxy formation during early epochs. To begin understanding the M81 spheroid, we are currently studying the globular cluster population using HST/WFPC2 multiband imaging and ground based optical spectroscopy. To complete this effort, we propose to use ACS/WFC to obtain deep (I, V-I) color magnitude diagrams (to the horizontal branch) of two fields in M81 - one dominated by thick disk stars and the other halo stars. These observations will provide tight constraints on the formation timescales and chemical enrichment history of the field star population. Combined with results on the globular clusters, we will reconstruct the early formation history of M81, and compare with those found for other nearby, massive galaxies. Because M81 is the earliest type spiral galaxy (Sab) available for such a detailed study, it provides a unique opportunity to probe the connection between elliptical halos and lower mass spiral spheroids. ------------------------------------------------------------------------------------ 10604( 3) - 05/11/05 09:06 - [ 2] Observations Description ------------------------ We will use the ACS/WFC to obtain deep V-I color magnitude diagrams of the halo of M81, the closest (3.6 Mpc) early-type (Sab) spiral galaxy. Since M81 has two close interacting companions (M82 and NGC 3077), we have carefully chosen our target field to avoid the HI bridges and other interaction material. Basen on the M81 structural analysis performed by Tikhonov et al. (2004), we have selected a halo field which is outside of the radius found by their analysis. We will use the F606W and F814W filters to make color magnitude diagrams, due to the additional sensitivity of the F606W filter over F555W. These filters have previous observations of Galactic globular clusters with the ACS/WFC which can be used for calibration. Based on previous work, we need to achieve a minimum S/N of 10 for stars in the red clump (M_V=0). Assuming the Cepheid distance modulus of 27.8 and A_V=0.2 for M81, we need to reach V=28 and I=27. In addition to stars in the red clump, we are interested in the morphology of horizontal branch stars. Because these are bluer (hotter) than red clump stars, additional time in the F814W filter relative to that in the F606W is required. Therefore, we observe the M81 halo field for 5 orbits in F606W, and 9 total orbits in F814W. The F814W orbits will be broken into 2 separate visits or 4 and 5 orbit durations. In addition to the primary ACS/WFC primary observations, coordinated parallels with WFPC2 were approved. These will be taken with the same filters. We have specified a range of possible spacecraft roll angles in order to optimize the location of the coordinated WFPC2 parallels. Our range of orientations is schedulable, and has been chosen to sample a somewhat more distant M81 halo field, so that we can explore metallicity gradients. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 10604( 3) - 05/11/05 09:06 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 M81-HALO- GALAXY, HALO RA=09H53M3.2000S +/- 0.1", J2000 V = 28.0 FLD1 DEC=+68D52'3.60" +/- 0.1" Coordinate Source: GUIDE_STAR_CATALOG 10604( 3) - 05/11/05 09:06 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.265 Line_Spacing 0.187 Coordinate_Frame POS-TARG Pattern_Orient 20.67 Angle_Between_Sides 69.05 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 10604( 3) - 05/11/05 09:06 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 70%; ORIENT 340.0D TO 359.9 D; ORIENT 0.0D TO 20.0 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 M81-HALO-FL ACS/WFC ACCUM WFC-FIX F814W CR-SPLIT=2 1 2494 S POS TARG 0, 0; PATTERN 1 D1 1-2; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFPC2 IMAGE WFALL-FIX F814W 1 2200 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 | ------------------------------------------------------------------------------------------------------------------------------------ M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 1 none none 1 1 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 1 none none 2 1 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 2 none none 1 2 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 2 none none 2 2 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 3 none none 1 3 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 3 none none 2 3 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 4 none none 1 4 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 4 none none 2 4 N/A ANY 2 WFPC2 IMAGE WFALL-FI F814W 1 none none 1 1 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 1 none none 2 1 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 2 none none 1 2 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 2 none none 2 2 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 3 none none 1 3 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 3 none none 2 3 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 4 none none 1 4 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 4 none none 2 4 N/A X 10604( 3) - 05/11/05 09:06 - [ 6] Visit: 02 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 70%; 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 M81-HALO-FL ACS/WFC ACCUM WFC-FIX F606W CR-SPLIT=2 1 2494 S POS TARG 0, 0; PATTERN 1 D1 1-2; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFPC2 IMAGE WFALL-FIX F606W 1 2200 S ------------------------------------------------------------------------------------------------------------------------------------ 3 M81-HALO-FL ACS/WFC ACCUM WFC-FIX F606W CR-SPLIT=2 1 2494 S POS TARG 0, 0.125; PAR 4 D1 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFPC2 IMAGE WFALL-FIX F606W 1 2200 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 | ------------------------------------------------------------------------------------------------------------------------------------ M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F606W 1 none none 1 1 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F606W 1 none none 2 1 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F606W 2 none none 1 2 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F606W 2 none none 2 2 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F606W 3 none none 1 3 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F606W 3 none none 2 3 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F606W 4 none none 1 4 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F606W 4 none none 2 4 N/A ANY 2 WFPC2 IMAGE WFALL-FI F606W 1 none none 1 1 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F606W 1 none none 2 1 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F606W 2 none none 1 2 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F606W 2 none none 2 2 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F606W 3 none none 1 3 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F606W 3 none none 2 3 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F606W 4 none none 1 4 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F606W 4 none none 2 4 N/A X M81-HALO-FLD1 3 ACS/WFC ACCUM WFC-FIX F606W none none none 1 5 N/A 10604( 3) - 05/11/05 09:06 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M81-HALO-FLD1 3 ACS/WFC ACCUM WFC-FIX F606W none none none 2 5 N/A ANY 4 WFPC2 IMAGE WFALL-FI F606W none none none 1 5 N/A X ANY 4 WFPC2 IMAGE WFALL-FI F606W none none none 2 5 N/A X 10604( 3) - 05/11/05 09:06 - [ 8] Visit: 03 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 70%; 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 M81-HALO-FL ACS/WFC ACCUM WFC-FIX F814W CR-SPLIT=2 1 2494 S POS TARG 0, 0; PATTERN 1 D1 1-2; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFPC2 IMAGE WFALL-FIX F814W 1 2200 S ------------------------------------------------------------------------------------------------------------------------------------ 3 M81-HALO-FL ACS/WFC ACCUM WFC-FIX F814W CR-SPLIT=2 1 2494 S POS TARG 0, 0.125; PAR 4 D1 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFPC2 IMAGE WFALL-FIX F814W 1 2200 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 | ------------------------------------------------------------------------------------------------------------------------------------ M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 1 none none 1 1 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 1 none none 2 1 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 2 none none 1 2 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 2 none none 2 2 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 3 none none 1 3 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 3 none none 2 3 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 4 none none 1 4 N/A M81-HALO-FLD1 1 ACS/WFC ACCUM WFC-FIX F814W 4 none none 2 4 N/A ANY 2 WFPC2 IMAGE WFALL-FI F814W 1 none none 1 1 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 1 none none 2 1 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 2 none none 1 2 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 2 none none 2 2 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 3 none none 1 3 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 3 none none 2 3 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 4 none none 1 4 N/A X ANY 2 WFPC2 IMAGE WFALL-FI F814W 4 none none 2 4 N/A X M81-HALO-FLD1 3 ACS/WFC ACCUM WFC-FIX F814W none none none 1 5 N/A 10604( 3) - 05/11/05 09:06 - [ 9] 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 | ------------------------------------------------------------------------------------------------------------------------------------ M81-HALO-FLD1 3 ACS/WFC ACCUM WFC-FIX F814W none none none 2 5 N/A ANY 4 WFPC2 IMAGE WFALL-FI F814W none none none 1 5 N/A X ANY 4 WFPC2 IMAGE WFALL-FI F814W none none none 2 5 N/A X 10604( 3) - 05/11/05 09:06 - [ 10] Summary Form for Proposal 10604 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC-FIX WFALL-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE; SCHED 70%; ORIENT 340.0D TO 359.9 D; ORIENT 0.0D TO 20.0 D POS TARG 0, 0; PATTERN 1 1-2; PAR 2 WITH 1 PCS MODE FINE; SCHED 70%; SAME ORIENT AS 01 POS TARG 0, 0.125; PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names M81-HALO-FLD1 ANY ------------------------------------------------------------------------------------------------------------------------------------