6477( 3) - 02/20/96 10:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6477 Version: 3 Check-in Date: 20-Feb-1996 10:08:52 1.Proposal Title: The Color-Magnitude Diagram of the Super- Metal-Rich Globular Cluster G198 in M31 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle STELLAR POPULATIONS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Pascale JABLONKA Observatoire de Paris, Section de Meudon CoI: Terry BRIDGES Institute of Astronomy, Cambridge N CoI: Andre MAEDER Observatoire de Geneve N CoI: Georges MEYLAN European Southern Observatory N CoI: Georges MEYNET Observatoire de Geneve N CoI: Ata SARAJEDINI Kitt Peak National Observatory N ------------------------------------------------------------------------------------ 6. Abstract We propose to observe the super-metal-rich globular cluster G198 in M31. We wish to obtain deep images in the F555W (V) and F814W (I) bands, taking advantage of the high spatial resolution and red sensitivity of the Planetary Camera of WFPC2, in order to construct a color-magnitude diagram for G198. With respect to the outstanding properties of this cluster, we will address primarily the question of its metallicity both on an absolute scale, by comparison with theoretical stellar evolutionary tracks, and on a relative scale, by comparison with a sample of clusters used as standards. The data we propose to obtain would provide essential input for theories of stellar evolution, star formation history, and models of star cluster and galaxy formation. ------------------------------------------------------------------------------------ 6477( 3) - 02/20/96 10:13 - [ 2] Observations Description ------------------------ As specified in the scientific justification, we need to resolve the HB stars in G198. Consequently, we plan to reach V~eq 26, with signal-to-noise ratio ~ 10 for unambiguous detection with good enough photometry in the CMD. The cluster position relatively close to the center of M31 (~2-3 arcmin) induces a rather high value of the sky surface brightness (~ 19 Vmag arcsec^-2; see Walterbos & Kennicutt, 1988, A&A, 198, 86). We plan to integrate 1.5 hours in both F555W (V) and F814W (I) filters. This requires 4 orbits with an optimized division in exposures which would provide a good orbit packing, while allowing of course for the GS acquisition and the readout overheads. Due to the multiplicity of exposures, cosmic-ray splits would not be necessary. The PC chip will be centered on the target cluster, for maximum spatial resolution there. The PC will be oriented to maximize the scientific output of the three surrounding WFC chips. Real Time Justification ----------------------- We need sub-pixel shifts in between frames. Because HST is undersampled, even by the PC, it becomes important to deal with this problem in our program. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6477( 3) - 02/20/96 10:13 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC224-G198 EXT-CLUSTER RA= 00H 42M 59.23S +/-0.2S, J2000 V = 16.0 DEC=41D 19' 19.21" +/-0.2", B-V = 1.24 PLATE-ID=0738 Comments: We shift the centering of the PC by 6 arcsec in alpha (cluster at 00H 42M 59.63S) in order to avoid a brigh star nearby. Coordinates need to be remeasured in the full gasp coordinate frame as the DSS for use in Phase II measurements is saturated. 6477( 3) - 02/20/96 10:13 - [ 4] Visit: 01 Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: We shift by 5.5 pixels between exposures. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC224-G198 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 1100S POS TARG 0.0,0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC224-G198 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO 2 1300S POS TARG 0.0,0.0 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC224-G198 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 1300S POS TARG 0.25047,-0.24047 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC224-G198 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO 2 1300S POS TARG 0.25047,-0.24047 ------------------------------------------------------------------------------------------------------------------------------------ 6477( 3) - 02/20/96 10:13 - [ 5] Summary Form for Proposal 6477 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F POS TARG 0.0,0.0 POS TARG 0.25047,-0.24047 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC224-G198 ------------------------------------------------------------------------------------------------------------------------------------