6104( 9) - 04/11/97 12:56 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6104 Version: 9 Check-in Date: 11-Apr-1997 12:53:33 1.Proposal Title: Deep Imaging of Globular Clusters in the Coma Ellipticals ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Galaxies & Clusters GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: WILLIAM E. HARRIS McMaster University CoI: David A. Hanes Queen's University N CoI: James E. Hesser Dominion Astrophysical Observatory N CoI: Christopher J. Pritchet University of Victoria N ------------------------------------------------------------------------------------ 6. Abstract We will use WFPC2 in V and I to image the globular cluster system around NGC4874, the central supergiant elliptical in the Coma Cluster, to a limiting magnitude V~eq 28. The three principal scientific goals are: (1) To measure the luminosity distribution of the globular clusters in the galaxy, and thus the mass distribution function of the clusters, to M_V(lim)~eq -7.0, fainter than the LF peak frequency or `turnover' point. (2) To obtain the total cluster population (specific frequencies S_N) of the galaxy, thus measuring the cluster formation efficiency and testing the (uncertain) ground-based observations that NGC 4874 has a high specific frequency like M87. (3) To measure the metallicity distribution function (MDF) of the clusters, including the cluster-to-cluster metallicity dispersion and the mean metallicity gradient within the system. These data will allow us to investigate the chemical enrichment history, mass distribution, and formation efficiency of globular clusters within NGC 4874, and they will extend our study of these phenomena to a much richer and denser galaxy environment than is accessible from ground-based imaging. ------------------------------------------------------------------------------------ 6104( 9) - 04/11/97 12:56 - [ 2] Observations Description ------------------------ We will position the Planetary Camera CCD near the center of NGC 4874 to obtain the best image scale for the innermost 15'' radius (or about 7 kpc) of the globular cluster system. The three WFC CCDs will then be used to study the wider-scale metallicity distribution and luminosity distribution of the clusters, out to R ~eq 30 kpc. The individual globular clusters will appear nearly starlike and thus easily separable from the majority of other objects in the field (dwarf galaxies in Coma, plus contaminating faint background galaxies). We will obtain exposures in two bands, F606W (V) and F814W (I). The V data will be used primarily for the deep GCLF study and spatial distribution, while the I images will be used to obtain accurate V-I colors and thus metallicities for the brighter clusters. Two spacecraft visits will be required to execute the program: one for the deep V exposure sequence, and the second for the deep I exposures and the short V,I exposures. It is essential for the second visit to return to the same orientation (roll angle) and zeropoint position to within 2 arcseconds, along with a consistent set of guidestars for both visits. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: ------------------------------------------------------------------------------------ 6104( 9) - 04/11/97 12:56 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4874 EXT-CLUSTER,GLOBULAR RA=12H 59M 35.7S +/- 2", J2000 V = V = 27.7 CLUSTER DEC=+27D 57' 38.0" +/- 2", PLATE +7180 B-V = 0.8 -ID=002K Comments: THE NUCLEUS OF THE GALAXY IS POSITIONED 5'' SOUTH OF THE PC1 CENTER. THIS CAN BE MODIFIED TO NORTH, EAST, OR WEST IF NECESSARY FOR GUIDE STAR SELECTION. INITIAL ORIENTATION ANGLE IS ARBITRARY. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982.387 0.0 0.0 0.0 6104( 9) - 04/11/97 12:56 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 2 1100 S POS TARG 0.0, 0.0 Comments: EXPOSURES 13-20 ARE AN 8 STEP SEQUENCE IN V AROUND AN OCTAGONAL PATTERN WITH 2.5 PIXEL STEPS BETWEEN EXPOSURES. ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 2 1300 S POS TARG 0.115, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 2 1300 S POS TARG 0.230, 0.115 ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 2 1300 S POS TARG 0.230, 0.230 ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 2 1300 S POS TARG 0.115, 0.345 ------------------------------------------------------------------------------------------------------------------------------------ 18 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 2 1300 S POS TARG 0.0, 0.345 ------------------------------------------------------------------------------------------------------------------------------------ 19 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 2 1300 S POS TARG -0.115, 0.230 ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 2 1300 S POS TARG -0.115, 0.115 ------------------------------------------------------------------------------------------------------------------------------------ 6104( 9) - 04/11/97 12:56 - [ 5] Visit: 02 Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: VISIT 2 MUST HAVE SAME ROLL ANGLE AS VISIT 1, AND SAME POSITION TO WITHIN 2 ARCSECONDS, ALONG WITH CONSISTENT SET OF GUIDE STARS. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC4874 WFPC2 IMAGE PC1-FIX F606W CR-SPLIT=NO 3 180 S Comments: SEQUENCE OF 3 X 180 SEC IN V. EXPOSURES 21-22 SHOULD TAKE UP ONE ORBIT. ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC4874 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 4 230 S Comments: SEQUENCE OF 4 X 230 SEC IN I ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC4874 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 2 1300 S POS TARG 0.0, 0.058 Comments: EXPOSURES 23-25 ARE A 3 X 2600 SEC SEQUENCE IN I AROUND A TRIANGLE PATTERN WITH 2.5 PIXEL STEPS ------------------------------------------------------------------------------------------------------------------------------------ 24 NGC4874 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 2 1300 S POS TARG -0.058, -0.058 ------------------------------------------------------------------------------------------------------------------------------------ 25 NGC4874 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 2 1300 S POS TARG 0.058, -0.058 ------------------------------------------------------------------------------------------------------------------------------------ 6104( 9) - 04/11/97 12:56 - [ 6] Summary Form for Proposal 6104 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Galaxies & Clusters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG 0.0, 0.0 POS TARG 0.115, 0.0 POS TARG 0.230, 0.115 POS TARG 0.230, 0.230 POS TARG 0.115, 0.345 POS TARG 0.0, 0.345 POS TARG -0.115, 0.230 POS TARG -0.115, 0.115 SAME ORIENT AS 01 POS TARG 0.0, 0.058 POS TARG -0.058, -0.058 POS TARG 0.058, -0.058 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC4874 ------------------------------------------------------------------------------------------------------------------------------------