6517( 7) - 01/15/97 13:21 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6517 Version: 7 Check-in Date: 15-Jan-1997 13:19:07 1.Proposal Title: The Formation of the Inner Galactic Halo ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle STELLAR POPULATIONS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: BRIAN CHABOYER STEWARD OBSERVATORY CoI: Taft Armandroff Kitt Peak National Observatory, NOAO N CoI: Ata Sarajedini Kitt Peak National Observatory, NOAO N ------------------------------------------------------------------------------------ 6. Abstract We propose to obtain WFPC2 observations of an inner halo globular cluster. These observations will be used to derive a precise colour-magnitude diagram in order to obtain an accurate age and hence, determine the formation chronology of the inner halo. The globular clusters chosen for observation is NGC 6652, a relatively metal- rich (Fe/H = -0.9) member of the inner halo which has been suggested to be extremely young. Obtaining an accurate age for this member of the inner halo will allow us to determine if the inner halo formed over an extended period of time, and if so, how long the formation process lasted. In order to reliably estimate the ages of these clusters, the location of the main sequence turn-off must be accurately determined. Given the extreme crowding and field contamination problems associated with observing these clusters, this is only possible with the spatial resolution of HST. ------------------------------------------------------------------------------------ Observations Description ------------------------ The following calculations are based on the successful results of the Zinn et al. (GO-5366) group who have obtained photometry with S/N ~ 50 at 2 magnitudes below the main sequence turnoff for Galactic globular clusters in order to study their ages. Note that the short exposures will be used to photometer the horizontal branch stars and to check the photometric zero-point against ground- based observations. For NGC 6652 (V(TO) ~ 19.5), we need 4 x 400s in F555W and 4 x 700s in F814W along with short exposures of 2 x 40s in F555W and 2 x 60s in F814W. Each orbit is 53 minutes in duration with 7.5 minutes needed for guide star acquisition leaving 45.5 minutes for science activities. The total exposure + overhead time will be 137 minutes for NGC 6652, Adding up these exposure times and adjusting them to fit into orbits means that we need 3 orbits to complete this program. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Taft Armandroff, Kitt Peak National Obervatory, P.O. Box 26732, 950 North Cherry Avenue, Tucson, AZ 85719 Ship Via: Email: tarmandroff@noao.edu , ------------------------------------------------------------------------------------ 6517( 7) - 01/15/97 13:21 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6652 STELLAR RA=18H 35M 45.7S +/- 0.1S,DEC=- J2000 V = -112 V = 8.62+/-0.1 CLUSTER,GLOBULAR 32D 59' 26" +/- 1" CLUSTER Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B1950 0.0 0.0 0.0 6517( 7) - 01/15/97 13:21 - [ 2] 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 NGC6652 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 3 23 S MAX DUR 100% POS TARG 0, 16 ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC6652 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 2 20 S MAX DUR 100% POS TARG 0, 16 ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC6652 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 3 20 S MAX DUR 100% POS TARG 0, -16 ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC6652 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 3 23 S MAX DUR 100% POS TARG 0, -16 ------------------------------------------------------------------------------------------------------------------------------------ 50 NGC6652 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 3 23 S MAX DUR 100% ------------------------------------------------------------------------------------------------------------------------------------ 60 NGC6652 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 3 20 S MAX DUR 100% ------------------------------------------------------------------------------------------------------------------------------------ 70 NGC6652 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 12 160 S ------------------------------------------------------------------------------------------------------------------------------------ 80 NGC6652 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 12 160 S ------------------------------------------------------------------------------------------------------------------------------------ 6517( 7) - 01/15/97 13:21 - [ 3] Summary Form for Proposal 6517 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN=15 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements MAX DUR 100% POS TARG 0,16 MAX DUR 100% POS TARG 0,-16 MAX DUR 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6652 ------------------------------------------------------------------------------------------------------------------------------------