6804( 7) - 02/25/98 10:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6804 Version: 7 Check-in Date: 25-Feb-1998 10:12:19 1.Proposal Title: Large Population Studies of Globular Clusters ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 6 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: FLAVIO FUSI PECCI Osservatorio Astronomico of Bologna CoI: Roberto Buonanno Osservatorio Astronomico di Roma N CoI: Carlo Corsi Osservatorio Astronomico di Roma N CoI: Gianni Marconi Osservatorio Astronomico di Roma N CoI: Robert T. Rood University of Virginia N CoI: Ben Dorman Goddard Space Flight Center N CoI: Wayne Landsman Goddard Space Flight Center N CoI: Francesco R. Ferraro Osservatorio Astronomico di Bologna N CoI: Carla Cacciari Osservatorio Astronomico di Bologna N ------------------------------------------------------------------------------------ 5. Abstract We aim at obtaining very accurate photometric data on 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 Cycles 4 & 5 we have been granted time to observe the intermediate metal-poor GGC M3 and the very low metallicity GGC M92. To complement these studies of metallicity effects in ``normal'' GGC's, we propose WFPC2 observations (in UV, U, V, I bands) of two ``second parameter'' GGC's, NGC 2808 & NGC 288. 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 tools for testing stellar evolutionary models (about the accuracy of the input physics, the reliability of canonical assumptions, etc.) and have a very wide applicability including: (1) the most accurate check of the ``stellar clock'' used in dating globular clusters; (2) a complete survey of 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. Adding \2p\ clusters to our sample will allow us to study possible age variations in the halo and to put \2p\ studies on a more physical basis. NGC 2808 is particularly interesting in that it is probably the best candidate in which to observe a breakdown of the canonical assumptions. ------------------------------------------------------------------------------------ 6804( 7) - 02/25/98 10:13 - [ 2] Observations Description ------------------------ We plan to obtain WFPC2 observations of the Galactic globular clusters NGC 2808 & NGC 288 whose main parameters are listed in the table below. Observations will be taken on the cluster cores in the 3 filters (F336W, F555W, F814W). A far-UV exposure is proposed for NGC 2808 (F160BW). This cluster was observed at 1500 A by UIT on Astro-2 (UIT-2) in March 1995 and shows a dense clump of sources in the center (r < 30") that are too crowded to measure on the ~ 4" resolution UIT image. Neither the ground-based optical photometry nor the UIT photometry is complete at the faint blue end of the HB. Our far-UV image will complement both the UIT-2 image which gives FUV fluxes in the outer cluster, and the mid-UV (F218W) image to be obtained by Djorgovski et al (GO 6095) in Cycle 5. We propose a mid-UV (F255W) image for NGC 288, not previously observed in the ultraviolet, because its HB tail does not extend as blue as that of NGC 2808. 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=30-50 in the V and I filters for a G0V star 2 mag below the turnoff; S/N=20 -30 in the U filter for a F0V star at the same magnitude; S/N=20 or more in the mid-UV filter F255W for A0 stars at the TO level; and S/N=20 or more in the far -UV filter F160W for B0 stars at the TO level. The V and I exposures will be divided 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. This observing sequence will be repeated at radial distance of 2.5 arcmin in NGC 2808. In addition, pairs of very deep V and I exposures will be taken at radial distance of 2.5 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 long exposures will be ``dithered'' on 2-3 positions in order to identify and remove hot pixels and cosmic rays, recover spatial resolution and improve the photometric sampling and accuracy. A very similar observing strategy was applied to the programs GO 5496 (cycle 4) on M3 and 5969 (cycle 5) on M92, of which the present proposal is a natural continuation. The exposure times have been estimated using our own exposure time calculator based on the WFPC2 1995 Handbook, since the ETC provided by the STScI on WWW gave systematically underestimated exposure times. Some basic parameters for the program clusters are listed in Table 1. Table 1. Globular Cluster Parameters. Object Vo(TO) Fe/H E(B-V) log(Rho) NGC2808 19.0 -1.37 0.24 4.6 NGC 288 18.6 -1.40 0.03 1.8 Real Time Justification ----------------------- None. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6804( 7) - 02/25/98 10:13 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: ------------------------------------------------------------------------------------ 6804( 7) - 02/25/98 10:13 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC2808 STELLAR RA=09H 12M 02.6S +/- 0.1S,DEC=- J2000 SURF(V) = 15.17+/-0.1 CLUSTER,GLOBULAR 64D 51' 47.0" +/- 1" B-V = 0.90 CLUSTER E(B-V) = 0.24 Comments: Above flux values refer to the integrated cluster, for ACQ purposes only. For individual stars see Observing Description 2 NGC288 STELLAR RA=00H 52M 45.5S +/- 0.1S,DEC=- J2000 SURF(V) = 20.00+/-0.1 CLUSTER,GLOBULAR 26D 35' 04.0" +/- 1" B-V = 0.66 CLUSTER E(B-V) = 0.03 Comments: Above flux values refer to the integrated cluster, for ACQ purposes only. For individual stars see Observing Description. These coords are the new ones measured by Carla Cacciari from the GASP/GSSS finder charts provided for the program and are meant to mark the approximate center of the cluster. 6804( 7) - 02/25/98 10:13 - [ 5] Visit: 01 Visit Priority: Visit Requirements: CVZ On Hold Comments: Additional Comments: no unused visibility should be left at the end of this visit; visit 2 should be scheduled immediately after visit 1 and use the leftover time, so that visit 1 and 2 fit into a total of 6 CVZ orbits. These are all CVZ orbits and parts of the same set of observations, pointing on two positions of the cluster offset by 150'' Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC2808 WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO,ATD-GAIN=15, 1 1600 S DITHER-TYPE=BOX ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC2808 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,DITHER-TYPE=LINE, 1 100 S DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC2808 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15,DITHER-TYPE=LINE, 1 120 S DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC2808 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15,CR-SPLIT=0.50 1 6 S MAX DUR ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC2808 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.50 1 14 S MAX DUR ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC2808 WFPC2 IMAGE PC1-FIX F160BW CR-SPLIT=NO,DITHER-TYPE=LINE, 1 1200 S DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ 6804( 7) - 02/25/98 10:13 - [ 6] Visit: 02 Visit Priority: Visit Requirements: CVZ;SAME ORIENT AS 1;SEQ 1-2 WITHIN 96H On Hold Comments: Additional Comments: This visit should be scheduled contiguously and immediately after visit 1, without leaving any unused visibility at the end of visit 1. Visit 1 and 2 should fit into a total of 6 CVZ orbits. These are all part of the same set of observations, on two different pointings of the cluster offset by 150"; visit 2 was introduced to allow for GS ACQ, because of the large offset in the POS TARG Special Requirement Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC2808 WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO,ATD-GAIN=15, 1 1600 S POS TARG 150.00,150.00 DITHER-TYPE=BOX ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC2808 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,DITHER-TYPE=LINE, 1 100 S POS TARG 150.00,150.00 DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC2808 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15,DITHER-TYPE=LINE, 1 120 S POS TARG 150.00,150.00 DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC2808 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15,CR-SPLIT=0.50 1 6 S SAME POS AS 15 MAX DUR ------------------------------------------------------------------------------------------------------------------------------------ 18 NGC2808 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.50 1 14 S SAME POS AS 15 MAX DUR ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC2808 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO,DITHER-TYPE=BOX 1 700 S POS TARG 150.00,150.00 ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC2808 WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO,DITHER-TYPE=BOX 1 900 S POS TARG 150.00,150.00 ------------------------------------------------------------------------------------------------------------------------------------ 6804( 7) - 02/25/98 10:13 - [ 7] Visit: 03 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC288 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC288 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 2.3 S MAX DUR ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 100 S ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 28 S ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 1 1.2 S MAX DUR 100% ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15,CR-SPLIT=0.5 1 24 S ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 1 140 S ------------------------------------------------------------------------------------------------------------------------------------ 19 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 1 140 S POS TARG 0.3535,0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 24 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 100 S SAME POS AS 19 ------------------------------------------------------------------------------------------------------------------------------------ 27 NGC288 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 1000 S SAME POS AS 19 ------------------------------------------------------------------------------------------------------------------------------------ 29 NGC288 WFPC2 IMAGE PC1-FIX F255W ATD-GAIN=7,CR-SPLIT=0.5, 1 700 S SAME POS AS 19 CR-TOLERANCE=0.0 ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 2 100 S POS TARG 0.707,0.707 ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC288 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 1700 S SAME POS AS 30 ------------------------------------------------------------------------------------------------------------------------------------ 38 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 2 140 S SAME POS AS 30 ------------------------------------------------------------------------------------------------------------------------------------ 6804( 7) - 02/25/98 10:13 - [ 8] Visit: 04 Visit Priority: Visit Requirements: SAME ORIENT AS 3; GROUP 3-4 WITHIN 1D On Hold Comments: Additional Comments: This visit was originally part of Visit 03 but a new visit was required due to the large POS TARG shift which requires new guide stars and a new guide star acquisition. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 100 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 230 S POS TARG 110,0 ------------------------------------------------------------------------------------------------------------------------------------ 101 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 40 S SAME POS AS 100 ------------------------------------------------------------------------------------------------------------------------------------ 102 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 1 40 S SAME POS AS 100 ------------------------------------------------------------------------------------------------------------------------------------ 103 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 1 160 S SAME POS AS 100 ------------------------------------------------------------------------------------------------------------------------------------ 104 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 1 160 S POS TARG 110.3535,0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 106 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 230 S SAME POS AS 104 ------------------------------------------------------------------------------------------------------------------------------------ 108 NGC288 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 200 S POS TARG 110.7070,0.7070 ------------------------------------------------------------------------------------------------------------------------------------ 110 NGC288 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15 1 160 S SAME POS AS 108 ------------------------------------------------------------------------------------------------------------------------------------ 6804( 7) - 02/25/98 10:13 - [ 9] Summary Form for Proposal 6804 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ATD-GAIN=15 DITHER-TYPE=BOX DITHER-LINE-STEPS=3 DITHER-TYPE=LINE CR-SPLIT=0.50 CR-SPLIT=0.5 CR-TOLERANCE=0.0 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ MAX DUR CVZ;SAME ORIENT AS 1;SEQ 1-2 WITHIN 96H POS TARG 150.00,150.00 SAME POS AS 15 MAX DUR MAX DUR 100% POS TARG 0.3535,0.3535 SAME POS AS 19 POS TARG 0.707,0.707 SAME POS AS 30 SAME ORIENT AS 3; GROUP 3-4 WITHIN 1D POS TARG 110,0 SAME POS AS 100 POS TARG 110.3535,0.3535 SAME POS AS 104 POS TARG 110.7070,0.7070 SAME POS AS 108 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W F555W F814W F160BW F255W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC2808 NGC288 ------------------------------------------------------------------------------------------------------------------------------------