6798( 4) - 07/30/97 16:38 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6798 Version: 4 Check-in Date: 30-Jul-1997 16:37:20 1.Proposal Title: The Early Evolution of Local Group Dwarf Irregular Galaxies ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle STELLAR POPULATIONS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: GRAEME SMITH UNIVERSITY OF CALIFORNIA CoI: Carl Grillmair Caltech/Jet Propulsion Laboratory N CoI: Jon Holtzman New Mexico State University N ------------------------------------------------------------------------------------ 6. Abstract The scientific aim of this proposal is to determine whether gas-containing dwarf irregular galaxies in the Local Group have significant populations of very ancient stars of age comparable to Population II stars in the Galaxy, and if so, whether the properties of these old populations vary with parent galaxy type. A critical diagnostic of a true Population II having both old age (14-16 Gyr) and low metallicity is taken to be the presence of an extended horizontal branch in a color- magnitude diagram. We propose to obtain WFPC2 images in the F555W and F814W bands of two of the nearest Local group dwarf irregulars, WLM and Phoenix, in order to construct color-magnitude diagrams capable of revealing an extended horizontal branch. The CM diagrams will also allow the V-I color distribution of the Population II red giant branch to be determined, from which the mean metallicity and the metallicity dispersion will be derived. ------------------------------------------------------------------------------------ Observations Description ------------------------ The sizes of the galaxies are well matched to the field of the WFPC2, so that only one pointing per galaxy is necessary. In order to optimise detection of an old red giant population in the target galaxies, fields will be chosen that are removed from H II regions and young star associations identified from ground- based studies. We will not be targeting observations to study the most recent episodes of star formation in these galaxies. Real Time Justification ----------------------- None. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6798( 4) - 07/30/97 16:38 - [ 2] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: ------------------------------------------------------------------------------------ 6798( 4) - 07/30/97 16:38 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WLM GALAXY, AMORPHOUS RA=0H 1M 59.3S, DEC=-15D 26' J2000 V=-116 V = 10.9 IRREGULAR, DWARF 00", REGION, R=5" B-V = 0.44 COMPACT Comments: V and B-V refer to integrated apparent magnitude and color. 2 PHOENIX GALAXY, DWARF COMPACT, RA= 1H 51M 06.3S, DEC=-44D 26' J2000 V = 13.2 DWARF SPHEROIDAL 40.9", REGION, R=5" Comments: V refers to integrated apparent magnitude. 6798( 4) - 07/30/97 16:38 - [ 4] Visit: 01 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 WLM WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO,ATD-GAIN=15 1 100.0 S IX ------------------------------------------------------------------------------------------------------------------------------------ 11 WLM WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 1300.0 SAME POS AS 10 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 12 WLM WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 1000.0 SAME POS AS 10 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 20 WLM WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO,ATD-GAIN=15 1 100.0 S SAME POS AS 10 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 21 WLM WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 1300.0 SAME POS AS 10 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 22 WLM WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 1100.0 SAME POS AS 10 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 30 WLM WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO,ATD-GAIN=15 1 100.0 S POS TARG 0.25,0.25 NO IX SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 31 WLM WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 1300.0 SAME POS AS 30 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 32 WLM WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 1000.0 SAME POS AS 30 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 40 WLM WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO,ATD-GAIN=15 1 100.0 S SAME POS AS 30 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 41 WLM WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 1300.0 SAME POS AS 30 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 42 WLM WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 1100.0 SAME POS AS 30 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 6798( 4) - 07/30/97 16:38 - [ 5] Visit: 02 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 110 PHOENIX WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO,ATD-GAIN=15 1 100.0 S IX ------------------------------------------------------------------------------------------------------------------------------------ 111 PHOENIX WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 1300.0 SAME POS AS 110 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 112 PHOENIX WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 1000.0 SAME POS AS 110 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 120 PHOENIX WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO,ATD-GAIN=15 1 100.0 S SAME POS AS 110 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 121 PHOENIX WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 1300.0 SAME POS AS 110 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 122 PHOENIX WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 1100.0 SAME POS AS 110 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 130 PHOENIX WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO,ATD-GAIN=15 1 100.0 S POS TARG 0.25,0.25 NO IX SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 131 PHOENIX WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 1300.0 SAME POS AS 130 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 132 PHOENIX WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 1000.0 SAME POS AS 130 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 140 PHOENIX WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO,ATD-GAIN=15 1 100.0 S SAME POS AS 130 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 141 PHOENIX WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 1300.0 SAME POS AS 130 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 142 PHOENIX WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 1100.0 SAME POS AS 130 NO SPLIT IX ------------------------------------------------------------------------------------------------------------------------------------ 6798( 4) - 07/30/97 16:38 - [ 6] Summary Form for Proposal 6798 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ATD-GAIN=15 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SAME POS AS 10 NO SPLIT POS TARG 0.25,0.25 NO SPLIT SAME POS AS 30 NO SPLIT SAME POS AS 110 NO SPLIT SAME POS AS 130 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names WLM PHOENIX ------------------------------------------------------------------------------------------------------------------------------------