5902( 0) - 07/18/95 18:32 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5902 Version: ********** Check-in Date: ********** 1.Proposal Title: Color-Magnitude Diagrams and the internal structure of the globular clusters NGC 5694 & NGC 5824 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Stellar Populations GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Gregory G. Fahlman University of British Columbia CoI: Christian H.B. Koenig University of British Columbia Y CoI: Harvey B. Richer University of British Columbia N CoI: Ian Thompson The Observatories, Carnegie Institute N Washington ------------------------------------------------------------------------------------ 6. Abstract High stellar densities are produced in the cores of globular clusters through dynamical evolution. Recently, it has become clear that the physical characteristics of the stars in such cores can be modified, leading to the appearance of anomalous stellar populations. A study of these populations is important for furthering our understanding of the dynamical evolution of star clusters. The high spatial resolution imaging provided by HST is essential for uncovering and studying these anomalous stars. We propose to use the WFPC2 to make UBV observations of the central regions of two highly concentrated clusters, NGC 5694 and NGC 5824 for the primary purpose of studying the anomalous stellar populations revealed by our ground based images. These show bright, relatively blue quasi-stellar knots in the cluster cores. A large number of bright stars appear to the blue of the AGB/RGB in the cluster CMDs but, due to extreme crowding, we are unable to determine whether blue straggler stars are also present. These two targets are in the outer halo of the galaxy and the proposed HST observations will have a spatial resolution approximately equivalent to the best ground based images of NGC 6397. A secondary goal is to determine the ages for the two clusters through isochrone fitting and by application of differential measurements relative to other clusters of similar metallicity. ------------------------------------------------------------------------------------ 5902( 0) - 07/18/95 18:32 - [ 2] Observations Description ------------------------ We will observe NGC 5824 and NGC 5694 in the WFPC2 U,B and V (F336W, F459W and F555W) filters. Our exposure times are adjusted to minimize or where possible avoid the detrimental effects of CCD saturation due to bright stars near the cluster center, but still achieve small photometric errors for the faint magnitude ranges necessary to fulfill our scientific goals. The stellar populations in NGC 5694 & NGC 5824 are in the same magnitude range ( V_HB=18.50 and 18.60 respectively), making the following exposure calculations valid for both targets. In U, B and V short exposures of 120 sec, 10 sec and 120 sec respectively are required to image the core of the cluster and the central knots without saturating. The remaining exposures of 5 * 60 sec, 3 * 500 sec and 3 * 400 sec in V,B and U, respectively, are sufficient to limit photometric errors to 0.1 mags in B and V, 2.5 V-mags below the cluster turnoff, and 0.1 mags in U at the turnoff. With the cluster center placed on the PC virtually none of the stars saturating during the longer exposures will be affecting the WF CCDs. Real Time Justification ----------------------- None. We have obtained UBV observations of NGC 5824 and NGC 5694 under arcsecond seeing conditions at Las Campanas. The data is of excellent quality as indicated above and will enable us to calibrate the WFPC2 data. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Christian H.B. Koenig*Department of Geophysics & Astronomy,*129-2219 Main Mall ,*University of BC,*Vancouver,*British Columbia V6T 1Z4 ,*Canada Ship Via: UPS Email: koenig@geop.ubc.ca, koenig@astro.ubc.ca , ------------------------------------------------------------------------------------ 5902( 0) - 07/18/95 18:32 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5694 STELLAR CLUSTER, RA=14H 36M 41.60S +/- 2.0S, DEC= 1950.0 V=14.765 Globular Cluster, -26D 19' 24.9" +/- 2.0" B-V=0.8 Nucleus, Knot, U-V=0.4 Undesignated, STAR, SURF-BKG(V)=16.5 Comments: Fluxes are upper limits for most luminous object 2 NGC5824 STELLAR CLUSTER, RA=15H 0M 53.75S +/- 2.0S, DEC=- 1950.0 V=14.765 Globular Cluster, 32D 52' 22.6" +/- 2.0" B-V=0.8 Nucleus, Knot, U-V=0.4 Undesignated, STAR, SURF-BKG(V)=16.5 Comments: Fluxes are upper limits for most luminous objects 5902( 0) - 07/18/95 18:32 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5694 WFPC2 IMAGE PC1-FIX F336W 1 120S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC5694 WFPC2 IMAGE PC1-FIX F336W 3 400S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC5694 WFPC2 IMAGE PC1-FIX F555W 5 60S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC5694 WFPC2 IMAGE PC1-FIX F555W 1 10S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC5694 WFPC2 IMAGE PC1-FIX F439W 1 120S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC5694 WFPC2 IMAGE PC1-FIX F439W 3 500S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 5902( 0) - 07/18/95 18:32 - [ 5] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5824 WFPC2 IMAGE PC1-FIX F336W 1 120S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC5824 WFPC2 IMAGE PC1-FIX F336W 3 400S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC5824 WFPC2 IMAGE PC1-FIX F555W 5 60S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC5824 WFPC2 IMAGE PC1-FIX F555W 2 10S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC5824 WFPC2 IMAGE PC1-FIX F439W 1 120S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC5824 WFPC2 IMAGE PC1-FIX F439W 3 500S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 5902( 0) - 07/18/95 18:32 - [ 6] Summary Form for Proposal 5902 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Stellar Populations ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W F555W F439W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5694 NGC5824 ------------------------------------------------------------------------------------------------------------------------------------