! Proposal 5899, submission 1 ! PI: Haldan Cohn ! Received Mon Apr 3 00:10:03 EDT 1995 ! From: pi33@stsci.edu ! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 5899,v 4.1 1995/12/29 15:51:11 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Marc Bremmer ! Phone: 410 338-4458 , E-mail: bremmer@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Date generated: Sat Dec 17 09:52:16 EST 1994 ! Proposal_Information ! Section 4 Title: The Central Structure of the Collapsed- Core Globular Clusters NGC 6284 and NGC 6293 Proposal_Category: GO Scientific_Category: Stellar Populations Cycle: 5 Investigators PI_name: Haldan Cohn PI_Institution: Indiana University CoI_Name: Phyllis Lugger CoI_Institution: Indiana University Contact: N CoI_Name: Jonathan Grindlay CoI_Institution: Harvard University Contact: N 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. Questions ! Free format text (please update) Observing_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: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: NGC6284-CENTER Alternate_Names: Description: STELLAR CLUSTER, GLOBULAR CLUSTER Position: RA=17H 4M 28.8S +/- 0.1S, ! Most common specification format is DEC=-24D 45' 53" +/- 1" ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", Equinox: J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=22.5, B-V=0.6 ! Include at least V and B-V Comments: Collapsed-core globular cluster Target_Number: 2 Target_Name: NGC6293-CENTER Alternate_Names: Description: STELLAR CLUSTER, GLOBULAR CLUSTER Position: RA=17H 10M 10.4S +/- 0.1S, ! Most common specification format is DEC=-26D 34' 54" +/- 1" ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", Equinox: J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=22.5, B-V=0.6 ! Include at least V and B-V Comments: Collapsed-core globular cluster ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling ! PCS MODE [Fine | Gyro] ! GUIDing TOLerance ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN