! HST Cycle 5 GO proposal 6104 Proposal_Information Title: Deep Imaging of Globular Clusters in the Coma Ellipticals Proposal_Category: GO Scientific_Category: Galaxies & Clusters Cycle: 5 Investigators PI_name: William E. Harris PI_Institution: McMaster University CoI_Name: David A. Hanes CoI_Institution: Queen's University Contact: N CoI_Name: James E. Hesser CoI_Institution: Dominion Astrophysical Observatory Contact: N CoI_Name: Christopher J. Pritchet CoI_Institution: University of Victoria Contact: N 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. Questions Observing_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: Fixed_Targets Target_Number: 1 Target_Name: NGC4874 Alternate_Names: Description: EXT-CLUSTER,GLOBULAR CLUSTER Position: RA=12H 59M 35.7S +/- 2", DEC=+27D 57' 38.0" +/- 2", PLATE-ID=002K Equinox: J2000 RV_or_Z: V = +7180 RA_PM: Dec_PM: Epoch: 1982.387 Annual_Parallax: Flux: V = 27.7, B-V = 0.8 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. Visits Visit_Number: 01 Visit_Requirements: Exposure_Number: 13 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1100S Special_Requirements: 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. Exposure_Number: 14 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG 0.115, 0.0 Exposure_Number: 15 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG 0.230, 0.115 Exposure_Number: 16 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG 0.230, 0.230 Exposure_Number: 17 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG 0.115, 0.345 Exposure_Number: 18 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG 0.0, 0.345 Exposure_Number: 19 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG -0.115, 0.230 Exposure_Number: 20 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG -0.115, 0.115 Visit_Number: 02 Visit_Requirements: SAME ORIENT AS 01 Visit_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. Exposure_Number: 21 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F606W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 3 Time_Per_Exposure: 180S Special_Requirements: Comments: SEQUENCE OF 3 X 180 SEC IN V. EXPOSURES 21-22 SHOULD TAKE UP ONE ORBIT. Exposure_Number: 22 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 4 Time_Per_Exposure: 230S Special_Requirements: Comments: SEQUENCE OF 4 X 230 SEC IN I Exposure_Number: 23 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: 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 Exposure_Number: 24 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG -0.058, -0.058 Exposure_Number: 25 Target_Name: NGC4874 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 2 Time_Per_Exposure: 1300S Special_Requirements: POS TARG 0.058, -0.058 Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address ! W. E. Harris ! Dept of Physics and Astronomy ! McMaster University ! Hamilton ON L8S 4M1 Canada Ship_Via: UPS