5899( 4) - 12/29/95 10:58 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5899 Version: 4 Check-in Date: 29-Dec-1995 10:51:15 1.Proposal Title: The Central Structure of the Collapsed- Core Globular Clusters NGC 6284 and NGC 6293 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Stellar Populations GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Haldan Cohn Indiana University CoI: Phyllis Lugger Indiana University N CoI: Jonathan Grindlay Harvard University N ------------------------------------------------------------------------------------ 6. Abstract We propose to obtain deep UBV WFPC2 imaging of the central regions of the collapsed- core globular clusters NGC 6284 and NGC 6293. Our CTIO 4 m U-band surface photometry places upper limits of <1" on the core radii of these clusters (Lugger, Cohn, & Grindlay 1995). WFPC2 imaging will enable us to study the central structure of these dense cluster cores by star count analysis, providing key tests of our theoretical understanding of collisional stellar systems containing binary stars. We will construct color-magnitude diagrams and analyze the radial distributions of individual stellar groups to assess evidence of mass segregation. These observations will be particularly useful for detecting centrally concentrated populations of blue stragglers, bright CVs, and other UV-excess objects. We will fit detailed Fokker- Planck models to these data, as well as carry out nonparametric analyses, in order to test key predictions of the theory of the dynamical evolution of dense stellar systems including globular clusters and galactic nuclei. A particular goal is to distinguish between a small, but resolved core (r_c ~ 1") and a core that is in a state of deep collapse (r_c << 1"). The dynamical modeling will constrain the dark remnant populations -- particularly of heavy white dwarfs and neutron stars -- in the central regions of these clusters. The deep stellar photometry in collapsed cluster cores needed for this program depends critically on the high angular resolution provided by the HST. We are carrying out detailed simulations of HST WFPC2 imaging of collapsed cores based on our Fokker-Planck models, in order to develop optimal techniques for extracting information on cluster structure from these data. The combination of HST star counts for the central regions of the clusters, from the PC and WF frames, with ground-based star counts for the remainder of the clusters from CTIO and WIYN imaging, and large sets of stellar velocities from WIYN multi-object spectroscopy, will allow us to study the global dynamics of these clusters. ------------------------------------------------------------------------------------ 5899( 4) - 12/29/95 10:58 - [ 2] Observations Description ------------------------ We propose to obtain UBV WFPC2 exposures of NGC 6284 and NGC 6293, with the exact centers of the clusters positioned at the center of the PC frame. We have carefully computed exposure times for the F336W, F439W, and F336W filters based on our CTIO photometry of stars in the central regions of these clusters. With three orbits allocated to each cluster, an average of 7 exposures can be obtained in each filter. We have specified one sufficiently short exposure in each filter to insure that no bright star in the PC field saturates. The sequence of 4-7 long exposures in each filter will provide comparable signal-to -noise in the three filters. We have carefully packed the exposures into the orbits to make optimal use of the target visibility time. The short and long exposures will be combined to correct for saturated pixels in the latter and to filter out cosmic rays. The combined exposures will reach V = 22-23 with an accuracy of 0.1 mag, in locations away from the very centers of the clusters. The magnitude limits are brighter at the cluster centers due to crowding, which raises the effective background against which faint stars are detected. We are investigating this effect with image simulations. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5899( 4) - 12/29/95 10:58 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6284- STELLAR CLUSTER, RA=17H 4M 28.8S +/- 0.1S, DEC=- J2000 V = 22.5 CENTER GLOBULAR CLUSTER 24D 45' 53" +/- 1" B-V = 0.6 Comments: Collapsed-core globular cluster 2 NGC6293- STELLAR CLUSTER, RA=17H 10M 10.4S +/- 0.1S, DEC=- J2000 V = 22.5 CENTER GLOBULAR CLUSTER 26D 34' 54" +/- 1" B-V = 0.6 Comments: Collapsed-core globular cluster 5899( 4) - 12/29/95 10:58 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC6284- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 1 4S NO SPLIT CENTER Comments: short V ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC6284- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 4 40S NO SPLIT CENTER Comments: long V ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 160S NO SPLIT CENTER Comments: short U ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC6284- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 1 30S NO SPLIT CENTER Comments: short B ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC6284- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 1 160S NO SPLIT CENTER Comments: long B ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 2 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 24 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC6284- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 5 160S NO SPLIT CENTER Comments: long B ------------------------------------------------------------------------------------------------------------------------------------ 32 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 5899( 4) - 12/29/95 10:58 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 33 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 5899( 4) - 12/29/95 10:58 - [ 6] 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC6293- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 1 2S NO SPLIT CENTER Comments: short V ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC6293- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 5 40S NO SPLIT CENTER Comments: long V ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC6293- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 100S NO SPLIT CENTER Comments: short U ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC6293- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC6293- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC6293- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 1 20S NO SPLIT CENTER Comments: short B ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC6293- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 1 160S NO SPLIT CENTER Comments: long B ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC6293- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 2 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 24 NGC6293- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC6293- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 5 160S NO SPLIT CENTER Comments: long B ------------------------------------------------------------------------------------------------------------------------------------ 32 NGC6293- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 5899( 4) - 12/29/95 10:58 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 33 NGC6293- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 5899( 4) - 12/29/95 10:58 - [ 8] 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC6284- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 1 4S NO SPLIT CENTER Comments: short V ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC6284- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 4 40S NO SPLIT CENTER Comments: long V ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 160S NO SPLIT CENTER Comments: short U ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC6284- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 1 30S NO SPLIT CENTER Comments: short B ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC6284- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 1 160S NO SPLIT CENTER Comments: long B ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 2 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 24 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC6284- WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 5 160S NO SPLIT CENTER Comments: long B ------------------------------------------------------------------------------------------------------------------------------------ 32 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S NO SPLIT CENTER Comments: long U ------------------------------------------------------------------------------------------------------------------------------------ 5899( 4) - 12/29/95 10:58 - [ 9] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 33 NGC6284- WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 600S END ORBIT NO SPLIT CENTER Comments: long U, end of orbit ------------------------------------------------------------------------------------------------------------------------------------ 5899( 4) - 12/29/95 10:58 - [ 10] Summary Form for Proposal 5899 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Stellar Populations ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements NO SPLIT END ORBIT NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F336W F439W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6284-CENTER NGC6293-CENTER ------------------------------------------------------------------------------------------------------------------------------------