6701( 5) - 04/24/97 19:49 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6701 Version: 5 Check-in Date: 24-Apr-1997 19:45:26 1.Proposal Title: Photometry of the globular cluster system of the Sagittarius dwarf galaxy ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle STELLAR POPULATIONS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: RODRIGO IBATA UNIVERSITY OF BRITISH COLUMBIA CoI: Gregory Fahlman Department of Astronomy, University of N British Columbia, Canada CoI: Gerard Gilmore Institute of Astronomy, Cambridge, UK N CoI: Michael Irwin Royal Greenwich Observatory, Cambridge, UK N CoI: Harvey Richer Department of Astronomy, University of N British Columbia, Canada ------------------------------------------------------------------------------------ 6. Abstract We propose to use the WFPC2 to obtain deep V (F555W) and I (F814W) band images of the globular clusters of the Sagittarius dwarf galaxy: M54 (NGC 6715), Ter 7, Ter 8 and Arp 2. Isochrone fits to these data will yield the accurate ages of M54, Ter 8 and the Sagittarius dwarf galaxy (Sgr). These age estimates are needed to model the dynamics and evolution of the Sgr system and its interaction with the Milky Way. Sgr is in the final stages of tidal disruption (Velazquez & White 1995), so its globular clusters will drift away from their parent galaxy and soon disperse into the Galactic halo. Therefore at least some of the globular clusters of giant spiral galaxies like the Milky Way will have been captured from tidally destroyed dwarf galaxies. This statement has fundamental and wide ranging implications for the formation and evolution of globular clusters and spiral galaxies. It is therefore essential to conduct a detailed and accurate comparative study of the stellar populations of the Sgr and Galactic globular clusters, as we propose here. This, in turn, will allow detailed modeling of the chemical and dynamical evolution of Sgr and its globular clusters. ------------------------------------------------------------------------------------ 6701( 5) - 04/24/97 19:49 - [ 2] Observations Description ------------------------ We are proposing to undertake a comparative study of the globular clusters of the Sagittarius dwarf galaxy with those of the Milky Way. This requires as much information on the stellar populations of the clusters as can be obtained in a reasonable time. We will use a single orbit (53 minutes at the declination of these clusters) per field per filter, to obtain S/N > 7 photometry down to V=26, which is sufficient to achieve our scientific goals. Data acquisition in each field should start with the F814W filter. (We have assumed colors appropriate for a G dwarf). The time budgets are as follows: F814W: 12 minutes for guide-star acquisition 4x(17 seconds) CCD clearing 4x(2 minutes) CCD readout 4x(1 minute) dithering which leaves 4x400 seconds of exposure. This gives S/N > 8 at I=25. F555W: 6 minutes 23 seconds for guide-star re- acquisition 4x(17 seconds) CCD clearing 4x(2 minutes) CCD readout 4x(1 minute) dithering which leaves 4x500 seconds of exposure. This gives S/N > 7 at V=26. The photometric reductions will be accomplished using the latest version of P. Stetson's DAOPHOT photometry package. Four frames each in V & I are sufficient to remove cosmic rays since the positions of the stellar images can be found on a frame which is the median of all eight frames in a field. Real Time Justification ----------------------- We request that for the M54 observations, the PC field be centered on the core of the cluster. Our team is conducting several parallel studies of the Sgr system. We have obtained high and medium resolution spectra at CTIO and the AAT for many hundred member stars, and taken photographic plates with the UK- Schmidt Telescope and successfully determined the proper motion of Sgr. These data are currently being modelled. We also have Ca II triplet line -strength measurements of velocity confirmed Sgr members and members of M54, from which we have derived accurate abundances. We are currently applying for time at the AAT to obtain medium resolution spectra to delimit the size and mass of this fascinating dwarf galaxy. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 6701( 5) - 04/24/97 19:49 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ARP2 STELLAR RA=19H 28M 44.1S +/- 5",DEC=-30D J2000 V = 26 CLUSTER,GLOBULAR 21' 14" +/- 5" CLUSTER Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0 0.0 0.0 2 TER7 STELLAR RA=19H 17M 43.7S +/- 5",DEC=-34D J2000 V = 26 CLUSTER,GLOBULAR 39' 27" +/- 5" CLUSTER Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0 0.0 0.0 3 TER8 STELLAR RA=19H 41M 45.0S +/- 5",DEC=-34D J2000 V = 26 CLUSTER,GLOBULAR 0' 1" +/- 5" CLUSTER Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0 0.0 0.0 4 GAL-185503- GALAXY,DWARF SPHEROIDAL RA=18H 55M 3.3S +/- 5",DEC=-30D J2000 V = 26 304242 42' 42" +/- 5" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0 0.0 0.0 5 NGC6715 STELLAR RA=18H 55M 3.3S +/- 5",DEC=-30D J2000 V = 26 CLUSTER,GLOBULAR 28' 42" +/- 5" CLUSTER Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0 0.0 0.0 6701( 5) - 04/24/97 19:49 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 100 ARP2 WFPC2 IMAGE WFALL-F F814W 5 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 110 ARP2 WFPC2 IMAGE WFALL-F F814W 1 260 S IX ------------------------------------------------------------------------------------------------------------------------------------ 150 ARP2 WFPC2 IMAGE WFALL-F F555W 5 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 160 ARP2 WFPC2 IMAGE WFALL-F F555W 1 350 S IX ------------------------------------------------------------------------------------------------------------------------------------ 6701( 5) - 04/24/97 19:49 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 200 TER7 WFPC2 IMAGE WFALL-F F814W 5 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 210 TER7 WFPC2 IMAGE WFALL-F F814W 1 260 S IX ------------------------------------------------------------------------------------------------------------------------------------ 250 TER7 WFPC2 IMAGE WFALL-F F555W 5 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 260 TER7 WFPC2 IMAGE WFALL-F F555W 1 350 S IX ------------------------------------------------------------------------------------------------------------------------------------ 6701( 5) - 04/24/97 19:49 - [ 6] Visit: 03 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 ------------------------------------------------------------------------------------------------------------------------------------ 300 TER8 WFPC2 IMAGE WFALL-F F814W 5 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 310 TER8 WFPC2 IMAGE WFALL-F F814W 1 260 S IX ------------------------------------------------------------------------------------------------------------------------------------ 350 TER8 WFPC2 IMAGE WFALL-F F555W 5 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 360 TER8 WFPC2 IMAGE WFALL-F F555W 1 350 S IX ------------------------------------------------------------------------------------------------------------------------------------ 6701( 5) - 04/24/97 19:49 - [ 7] Visit: 04 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 ------------------------------------------------------------------------------------------------------------------------------------ 400 GAL-185503- WFPC2 IMAGE WFALL-F F814W 5 300 S 304242 IX ------------------------------------------------------------------------------------------------------------------------------------ 410 GAL-185503- WFPC2 IMAGE WFALL-F F814W 1 260 S 304242 IX ------------------------------------------------------------------------------------------------------------------------------------ 450 GAL-185503- WFPC2 IMAGE WFALL-F F555W 5 300 S 304242 IX ------------------------------------------------------------------------------------------------------------------------------------ 460 GAL-185503- WFPC2 IMAGE WFALL-F F555W 1 350 S 304242 IX ------------------------------------------------------------------------------------------------------------------------------------ 500 NGC6715 WFPC2 IMAGE PC1-FIX F814W 5 300 S ------------------------------------------------------------------------------------------------------------------------------------ 510 NGC6715 WFPC2 IMAGE PC1-FIX F814W 1 260 S ------------------------------------------------------------------------------------------------------------------------------------ 550 NGC6715 WFPC2 IMAGE PC1-FIX F555W 5 300 S ------------------------------------------------------------------------------------------------------------------------------------ 560 NGC6715 WFPC2 IMAGE PC1-FIX F555W 1 350 S ------------------------------------------------------------------------------------------------------------------------------------ 6701( 5) - 04/24/97 19:49 - [ 8] Visit: 13 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 ------------------------------------------------------------------------------------------------------------------------------------ 300 TER8 WFPC2 IMAGE WFALL-F F814W 5 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 310 TER8 WFPC2 IMAGE WFALL-F F814W 1 260 S IX ------------------------------------------------------------------------------------------------------------------------------------ 350 TER8 WFPC2 IMAGE WFALL-F F555W 5 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 360 TER8 WFPC2 IMAGE WFALL-F F555W 1 350 S IX ------------------------------------------------------------------------------------------------------------------------------------ 6701( 5) - 04/24/97 19:49 - [ 9] Summary Form for Proposal 6701 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ARP2 TER7 TER8 GAL-185503-304242 NGC6715 ------------------------------------------------------------------------------------------------------------------------------------