5905( 18) - 04/23/97 16:43 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5905 Version: 18 Check-in Date: 23-Apr-1997 16:41:18 1.Proposal Title: The Stellar Halo Metallicity Distribution of the Giant Elliptical NGC 5128 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Stellar Populations GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Gretchen L.H. Harris UNIVERSITY OF WATERLOO CoI: William E. Harris McMaster University N ------------------------------------------------------------------------------------ 6. Abstract We intend to measure the metallicity distribution function of the stellar halo of the nearby (d=3.5 Mpc) giant E0 galaxy NGC 5128 by direct color-magnitude photometry of its old red-giant stars. These data will allow us to determine accurately for the first time the mean metallicity and metallicity range of the oldest and most metal- poor field stars in a large elliptical galaxy, and thus constrain the level of enrichment which occurred during the earliest star formation. For the first time, we will then be able to compare the chemical enrichment history of giant E galaxies with galaxies of other types in the Local Group (spirals, dwarf ellipticals, and irregulars). ------------------------------------------------------------------------------------ 5905( 18) - 04/23/97 16:43 - [ 2] Observations Description ------------------------ NGC 5128 is 3.4 magnitudes more distant than M31. Our intention is to image one field at moderately large radius from the center of NGC 5128 at a projected distance corresponding to 20 kpc from the galaxy center. This field will be used to obtain direct color-magnitude photometry of the red-giant stars in the NGC 5128 halo, and thus to measure the metallicity distribution function of the halo. The standard V,I bands will be used. Our target field is to be centered near one of the known globular clusters belonging to NGC 5128 (number C44, Fe/H = -1.4). Comparison of the CMD's for the halo field and for the globular cluster itself will provide additional direct information on any systematic difference in the RGB loci between them. We will center the Planetary Camera CCD on the globular cluster. If the brightest red giants in NGC 5128 are similar to those in M31, they should resolve at V(RGB tip) = 26.4; however, they are likely to be up to half a magnitude fainter since the mean metallicity in the giant elliptical should be higher than in M31. To allow for this, we set a target V = 27.0 at high S/N. For each filter (V,I) we will obtain a 5 x 2400 sec and 4 x 200 sec exposure series for a total of 10 orbits. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: ------------------------------------------------------------------------------------ 5905( 18) - 04/23/97 16:43 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5128-C44 EXT-CLUSTER,GLOBULAR RA=13H 22M 35.6S +/- 2", DEC=- 1950 V = +550 V = 27.0 CLUSTER 43D 03' 49" +/- 2" B-V = 1.6 Comments: TARGET V MAGNITUDE CORRESPONDS TO RED GIANT STARS IN GALAXY HALO 5905( 18) - 04/23/97 16:43 - [ 4] Visit: 01 Visit Requirements: ORIENT 125D TO 125D On Hold Comments: Additional Comments: POSITION ANGLE OF U3 AXIS = 135D N THROUGH E; ORIENTATION CAN BE +/- 30D ABOUT NOMINAL. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC5128-C44 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 2 1200 S POS TARG 0,0 Comments: EXPOSURES 11-19 ARE A 5-STEP SEQUENCE WITH 2.5-PIXEL STEPS ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC5128-C44 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 2 1300 S POS TARG 0.341, -0.227 ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC5128-C44 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 2 1300 S POS TARG 0.227, 0.114 ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC5128-C44 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 2 1300 S POS TARG -0.114, 0.341 ------------------------------------------------------------------------------------------------------------------------------------ 19 NGC5128-C44 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 2 1300 S POS TARG -0.227, -0.114 ------------------------------------------------------------------------------------------------------------------------------------ 5905( 18) - 04/23/97 16:43 - [ 5] Visit: 02 Visit Requirements: ORIENT 125D TO 125D On Hold Comments: Additional Comments: VISIT 2 MUST HAVE SAME ROLL ANGLE AS VISIT 1, AND SAME POSITION TO WITHIN 2 ARCSECONDS, ALONG WITH CONSISTENT SET OF GUIDE STARS. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC5128-C44 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 1200 S POS TARG 0,0 Comments: EXPOSURES 21-29 ARE A 5-STEP SEQUENCE WITH 2.5-PIXEL STEPS ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC5128-C44 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 1300 S POS TARG 0.341, -0.227 ------------------------------------------------------------------------------------------------------------------------------------ 25 NGC5128-C44 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 1300 S POS TARG 0.227, 0.114 ------------------------------------------------------------------------------------------------------------------------------------ 27 NGC5128-C44 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 1300 S POS TARG -0.114, 0.341 ------------------------------------------------------------------------------------------------------------------------------------ 29 NGC5128-C44 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 1300 S POS TARG -0.227, -0.114 ------------------------------------------------------------------------------------------------------------------------------------ 32 NGC5128-C44 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 200 S POS TARG 0.0, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 33 NGC5128-C44 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 200 S SAME POS AS 32 ------------------------------------------------------------------------------------------------------------------------------------ 34 NGC5128-C44 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 200 S POS TARG 0.341, -0.227 ------------------------------------------------------------------------------------------------------------------------------------ 35 NGC5128-C44 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 200 S SAME POS AS 34 ------------------------------------------------------------------------------------------------------------------------------------ 5905( 18) - 04/23/97 16:43 - [ 6] Summary Form for Proposal 5905 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Stellar Populations ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 125D TO 125D POS TARG 0,0 POS TARG 0.341, -0.227 POS TARG 0.227, 0.114 POS TARG -0.114, 0.341 POS TARG -0.227, -0.114 POS TARG 0.0, 0.0 SAME POS AS 32 SAME POS AS 34 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5128-C44 ------------------------------------------------------------------------------------------------------------------------------------