9404( 3) - 08/16/02 12:52 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9404 Version: 3 Check-in Date: 16-Aug-2002 12:51:55 1.Proposal Title: Spatially Resolved Stellar Populations in Two z~2.5 Gravitational Arcs ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: David Thompson California Institute of Technology CoI: Marcin Sawicki California Institute of Technology N ------------------------------------------------------------------------------------ 5. Abstract We propose to use ACS and NICMOS to observe two gravitationally lensed galaxies at z~2.5. We will combine these data with existing archival and scheduled GTO observation to make spatially resolved maps of color, dust, and age for these objects. We will then use these maps to study the properties of individual star- forming regions within these galaxies, to search for an underlying old stellar population between the knots of active star formation, and to test previous HST and ground-based studies which have hitherto relied on spatially unresolved colors alone to study stellar population in high redshift star-forming galaxies. Ours will be the first study of stellar populations of Lyman Break Galaxies on sub-galactic scales, and will give important new insights into the way that these high-$z$ galaxies are assembled. ------------------------------------------------------------------------------------ 9404( 3) - 08/16/02 12:52 - [ 2] Observations Description ------------------------ Our targets are the second and third brightest (after cB58) gravitationally lensed z~2.5 galaxies currently known, and are representative of the LBG population. Considerable HST data exists or will be obtained for both of our targets. Abell 2218 is a well-studied cluster, and deep WFPC-2 imaging including the arc already exists in the F450W, F606W, F702W, and F814W filters. The CL1053+5735 cluster (which includes the arc) is targeted by an ACS/WFC GTO observation, with deep images in the F775W and F850LP filters scheduled. We propose deep observations using NICMOS in the F160W (H band) filter for our two targets. This will provide the photometry at a restframe wavelength of ~4700A, on the red side of the redshifted Balmer break. To get useful data on the fainter extended emission, our goal is to reach a surface brightness limit of H~22 (Vega) mag/sq.arcsec with 10% accuracy in the photometry. This can be reached in three orbits using NIC3 if the dark current is high, and NIC2 if the dark current is low (see below). In addition, we propose a 2-orbit ACS exposure of CL1053+5735 in the F606W filter, supplementing GTO observations of this source and giving us a better measurement of strength of the Balmer break. Scaling from the (V-H) colors of both arcs, our surface brightness limit is V~25 (Vega) mag/sq.arcsec with 10% accuracy per resolution element at H, which is about 3 sigma per ACS/WFC pixel. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ON HOLD requirement for NICMOS observations removed 15AUG02, and the NIC2 camera was selected instead of NIC3. We set up these NICMOS observations for NIC3 under the assumption that the dark current would be at the high end of the estimates after installation of the cooling system. Should the cryocooler work better than anticipated, it would be scientifically preferable to make these observations using NIC2. The NIC2 camera fully samples the diffraction limit of HST at 1.6 microns, but can only reach the necessary surface-brightness limits if the dark current is low. The exposure times and observing templates remain the same. ------------------------------------------------------------------------------------ 9404( 3) - 08/16/02 12:52 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CL1053+5735- Cluster of Galaxies, RA=10H 53M 47.36S +/- 0.5", J2000 Z=2.57 V = 22.0+/-0.1 ARC Gravitational Lens DEC=+57D 35' 13.9" +/- 0.5", H = 19.3+/-0.06 PLATE-ID=01OJ J = 404+/-20e-20 V-R = 0.2+/-0.2 J-K = 1.6+/-0.1 SURF(V) = 25.0+/-0.2 SURF(H) = 22.0+/-0.2 E(B-V) = 0.4+/-0.1 Coordinate Source: IMAGE_TIED_TO_GSC_FRAME Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 2 ABELL2218- Cluster of Galaxies, RA=16H 35M 49.82S +/- 0.5", J2000 Z=2.515 V = 21.2+/-0.2 ARC Gravitational Lens DEC=+66D 13' 03.0" +/- 0.5", H = 18.7+/-0.6 PLATE-ID=034O J = 246+/-15e-20 B-V = 0.8+/-0.2 J-K = 2.1+/-0.6 SURF(V) = 25.0+/-0.2 SURF(H) = 22.0+/-0.2 E(B-V) = 0.3+/-0.1 Coordinate Source: IMAGE_TIED_TO_GSC_FRAME Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 9404( 3) - 08/16/02 12:52 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 701 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.265 Coordinate_Frame POS-TARG Pattern_Orient 20.67 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 702 Primary_Pattern Secondary_Pattern Pattern_Type NIC-SKY-SPIRAL-DITH-CHOP NIC-SKY-SPIRAL-DITH-CHOP Pattern_Purpose DITHER BACKGROUND Number_Of_Points 6 2 Point_Spacing 1.4625 6.86 Coordinate_Frame POS-TARG CELESTIAL Pattern_Orient 201.80 201.80 Center_Pattern YES NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 703 Primary_Pattern Secondary_Pattern Pattern_Type NIC-SKY-SPIRAL-DITH-CHOP NIC-SKY-SPIRAL-DITH-CHOP Pattern_Purpose DITHER BACKGROUND Number_Of_Points 6 2 Point_Spacing 1.4625 9.75 Coordinate_Frame POS-TARG CELESTIAL Pattern_Orient 309.68 309.68 Center_Pattern YES NO ------------------------------------------------------------------------------------------------------------------------------------ 9404( 3) - 08/16/02 12:52 - [ 5] Visit: 01 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 CL1053+5735 ACS/WF ACCUM WFC1 F606W CR-SPLIT=NO 2 600 S PATTERN 701 -ARC C ------------------------------------------------------------------------------------------------------------------------------------ 9404( 3) - 08/16/02 12:52 - [ 6] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Pattern 702 works for either NIC2 or NIC3. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CL1053+5735 NIC2 MULTIAC NIC2-FI F160W SAMP-SEQ=STEP64,NSAMP=19 1 DEF PATTERN 702 -ARC CUM X Comments: Pattern 702 keeps CL1053+5735-ARC on NIC2 camera ------------------------------------------------------------------------------------------------------------------------------------ 9404( 3) - 08/16/02 12:52 - [ 7] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Pattern 703 works for either NIC2 or NIC3. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2218-A NIC2 MULTIAC NIC2-FI F160W SAMP-SEQ=STEP64,NSAMP=19 1 DEF PATTERN 703 RC CUM X Comments: Pattern 703 keeps ABELL2218-ARC on NIC2 camera ------------------------------------------------------------------------------------------------------------------------------------ 9404( 3) - 08/16/02 12:52 - [ 8] Summary Form for Proposal 9404 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1 NIC2-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC NIC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO NSAMP=19 SAMP-SEQ=STEP64 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 701 PATTERN 702 PATTERN 703 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W F160W ------------------------------------------------------------------------------------------------------------------------------------ Target Names CL1053+5735-ARC ABELL2218-ARC ------------------------------------------------------------------------------------------------------------------------------------