5969( 5) - 11/21/95 18:36 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5969 Version: 5 Check-in Date: ********** 1.Proposal Title: Large Population Studies of Globular Clusters ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Stellar Populations GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Flavio Fusi Pecci Osservatorio Astronomico CoI: Ben Dorman University of Virginia N CoI: Francesco R. Ferraro Osservatorio Astronomico di Bologna N CoI: Carla Cacciari Osservatorio Astronomico di Bologna Y CoI: Luciana Federici Osservatorio Astronomico di Bologna N CoI: Roberto Buonanno Osservatorio Astronomico di Roma N CoI: Carlo Corsi Osservatorio Astronomico di Roma N CoI: Giacinto Iannicola Osservatorio Astronomico di Roma N CoI: Robert T. Rood University of Virginia N ------------------------------------------------------------------------------------ 6. Abstract Our long term goal is to obtain very accurate photometric data of a complete sample of Post-Main Sequence (PMS) stars over the entire area of the cluster for a sample of ``prototype'' Galactic Globular Cluster (GGCs). During Cycle 4, 6 hours have been allocated to this program for observing the intermediate metallicity GGC M3. With the present program we shall take WFPC2 observations (in UV, U, V, and I bands) of M92, a very low metallicity GGC. The acquisition of a complete sample of PMS stars will allow us to construct Luminosity Functions (LFs) of stars in any PMS phase. LFs are the most powerful observable tool for testing stellar evolutionary models (e.g. the accuracy of the input physics, the reliability of canonical assumptions, etc.) and have useful applications in several areas, providing, e.g., the most accurate check of the ``stellar clock'' used in dating globular clusters. Our large samples also survey very fast evolutionary and rare (trace) stellar types (e.g. UV-bright stars, blue stragglers, binaries) along with their radial distributions, which will provide fundamental information for internal cluster dynamics and for the origin of UV light from elliptical galaxies. In addition, a pair of very deep exposures in V,I will be taken at two external positions, where the crowding is less severe. These will be used to study the faint end of the luminosity and mass functions of main sequence stars as a function of radial distance. ------------------------------------------------------------------------------------ 5969( 5) - 11/21/95 18:36 - [ 2] Observations Description ------------------------ We propose to obtain WFPC2 observations of the Galactic globular cluster M92 (whose main parameters are listed below) using 4 filters, i.e. F255W, F336W, F555W, F814W. The PC will be positioned on the cluster center and will cover an area of approximately 17 arcsec radius at the higher spatial resolution, while the WFC will cover an additional external area of approximately 2.5 arcmin radius over about 3/4 of the cluster, at a lower spatial resolution. Its lower space resolution is adequate to our needs thanks to the decreased stellar crowding. Ground-based CCD observations will cover the external part of the cluster, the two together providing as complete a mapping as can presently be obtained. Thanks to the restored HST optical performances it will be possible to detect and measure individual stars in all parts of the cluster, including the very central regions. Since the primary aim of this program is to obtain accurate photometric measurements for all the evolved stars, the observations have been planned to optimize both the degree of completeness (down to a fixed magnitude limit, even at the very center of the cluster) and the photometric quality of the individual measures. Hence, the adopted exposure times are adequate to reach S/N=50 in the V and I filters and S/N=30 in the U filter for a G0V star 2 mag below the turnoff, and S/N=10 in the UV filter F255W for F0 stars at the TO level. The V and I exposures will be subdivided into sets of sub-exposures short enough to avoid severe blooming from the brightest (V~13) M0 giants, which would introduce some degree of incompleteness and limit accuracy especially in the very crowded central regions. A few very short V and I exposures will also be taken for non-saturated photometry of the brighest part of the CM diagram. In addition, pairs of very deep V and I exposures will be taken at radial distances of 1.3 and 2.6 arcmin from the cluster center, in order to study the faintest part of the luminosity and mass functions (around absolute luminosity M(V)=+11 and mass M=0.10 Mo), as a function of radial distance. This will provide important information on the structure and dynamics of the cluster. The exposure times have been computed by adopting a readout noise of rn = 14e in the U, V, and I bands and rn = 7e in the UV band. The parameters used for the S/N (or exposure time) calculation are those specified in the WFPC2 Handbook, Version 2.0 May 1994, using the algorithm (S/N)^2=I^2/(I+B) since our observations are not background-dominated. All exposures will be ``dithered'' by 14.5 diagonal pixels in the PC, in order to identify and remove hot pixels and cosmic rays, recover spatial resolution and improve the photometric sampling and accuracy. NGC 6341 (M92): V(TO)=19 E(B- V)=0.02 [Fe/H]=-2.15 Log Rho=3.6 Real Time Justification ----------------------- None Calibration Justification ------------------------- No non-standard calibration observations are needed, however see the Observing Description section above for dithering. Additional Comments ------------------- ------------------------------------------------------------------------------------ 5969( 5) - 11/21/95 18:36 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5969( 5) - 11/21/95 18:36 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6341 STELLAR CLUSTER, RA=17H 17M 7.3S +/- 0.1S, 2000 SURF(V)=15.46 +/- 0.1 GLOBULAR CLUSTER DEC=+43D 8' 11.0" +/- 1" B-V=0.62 E(B-V)=0.02 Comments: Above flux values refer to the integrated cluster, for ACQ purposes only. For individual stars see observing description. 5969( 5) - 11/21/95 18:36 - [ 5] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6341 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15, CR 1 2000S -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6341 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15, CR 1 200S -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6341 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15, CR 1 2.4S -SPLIT=0.50 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC6341 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15, CR 1 4S -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC6341 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15, CR 2 140S -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC6341 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=0.5 1 1100S END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC6341 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15, CR 1 2.4S POS TARG 0.467, 0.467 -SPLIT=0.50 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC6341 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15, CR 1 1800S POS TARG 0.467, 0.467 -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC6341 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15, CR 1 200S POS TARG 0.467, 0.467 -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC6341 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15, CR 1 200S POS TARG 0.467, 0.467 -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC6341 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15, CR 1 140S POS TARG 0.467, 0.467 -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC6341 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15, CR 1 4S POS TARG 0.467, 0.467 -SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC6341 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=0.5 1 1300S POS TARG 0.467, 0.467; END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC6341 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5 1 1100S POS TARG 77.78, 77.78 ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC6341 WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=0.5 1 1100S POS TARG 77.78, 77.78; END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC6341 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5 1 1100S POS TARG 78.247, 78.247 ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC6341 WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=0.5 1 1300S POS TARG 78.247, 78.247; END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 18 NGC6341 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5 1 900S POS TARG 155.56, 155.56 ------------------------------------------------------------------------------------------------------------------------------------ 5969( 5) - 11/21/95 18:36 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 19 NGC6341 WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=0.5 1 1000S POS TARG 155.56, 155.56; END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC6341 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5 1 1100S POS TARG 156.027, 156.027 ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC6341 WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=0.5 1 1300S POS TARG 156.027, 156.027; END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 5969( 5) - 11/21/95 18:36 - [ 7] Summary Form for Proposal 5969 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN=15 CR-SPLIT=0.5 CR-SPLIT=0.50 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Stellar Populations ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements END ORBIT POS TARG 0.467, 0.467 POS TARG 0.467, 0.467; END ORBIT POS TARG 77.78, 77.78 POS TARG 77.78, 77.78; END ORBIT POS TARG 78.247, 78.247 POS TARG 78.247, 78.247; END ORBIT POS TARG 155.56, 155.56 POS TARG 155.56, 155.56; END ORBIT POS TARG 156.027, 156.027 POS TARG 156.027, 156.027; END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W F814W F555W F255W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6341 ------------------------------------------------------------------------------------------------------------------------------------