6699( 10) - 11/11/96 10:00 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6699 Version: 10 Check-in Date: 11-Nov-1996 09:56:46 1.Proposal Title: The Globular Cluster Systems of the Dwarf Elliptical Galaxies NGC 185 and NGC 205 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle STELLAR POPULATIONS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: DOUGLAS GEISLER KITT PEAK NATIONAL OBSERVATORY CoI: Ata Sarajedini Kitt Peak National Observatory N CoI: Taft Armandroff Kitt Peak National Observatory N CoI: Gary Da Costa Australian National University N CoI: Myung Gyoon Lee Seoul National University N ------------------------------------------------------------------------------------ 6. Abstract We propose to carryout a general reconnaissance of the properties of globular clusters in two Local Group dwarf elliptical galaxies: NGC 185 and NGC 205. Each of these galaxies possesses its own small coterie of globular clusters, which can be as useful as those in our own Galaxy for studying early galaxy formation history, but whose horizontal branches are well beyond the reach of ground-based telescopes. In particular, we will observe a sample of five clusters in each galaxy and determine their metallicities and HB morphologies from (V,V-I) color-magnitude diagrams. These clusters will be placed in the Fe/H:(B-R)/(B+V+R) diagram, along with analogous clusters in other Local Group galaxies with similar data. This analysis will allow us to study the development of these individual cluster systems and, more importantly, to compare and contrast the formation and early evolutionary histories of galaxies of different mass and morphological type. These will be the first data of this type for globular clusters in a dwarf, and nucleated dwarf, elliptical galaxy. Our data will also be used to estimate the mean cluster system metallicity and to investigate the variation of the HB magnitude with metal abundance. We will also measure structural parameters for each cluster. A final bonus will be an exploration of the mean metallicity, metallicity spread and HB morphology of the field population in a variety of regions in each galaxy. ------------------------------------------------------------------------------------ Observations Description ------------------------ These galaxies both have a visual distance modulus of (m- M)_V~ 24.5, implying that the HB stars of a typical cluster have V~ 25.3. We require sufficient photometric accuracy at this level to determine the mean magnitude of the HB to ~ 0.1 mag. We also desire to determine the metallicity to a precision of ~ 0.15 dex. From Sarajedini (1994), this requires determining the position of (V-I)_g, the intersection of the giant and horizontal branches (with a value of ~ 1.0), to a precision of about 0.015 mag. Given the large number of stars expected to inhabit this region (~ 100), this requires a (V-I) color accuracy per star of ~ 0.15 at the red end of the HB. Given these errors, Sarajedini (1994) indicates we can also derive the reddening E(V-I) to within ~ 0.03. Finally, in order to unequivocally identify blue HB stars (with (V-I)~ 0) as such requires S/N \\gtsim 5 in both filters. For a star at the blue end of the horizontal part of the HB, this is not a problem. However, given the metal-poor nature of these clusters, it is anticipated that several of them may exhibit the very long drooping faint blue HB exemplified by that of M15. We have examined the color- magnitude diagram of M15 and explored how faint one is required to go in order to recover the value of C (the HB morphology index) with sufficient accuracy. We find that if one goes only ~ 1 mag below the HB, many blue stars are missed; however, because of the high percentage of blue stars on the HB in such a metal -poor cluster, the derived value of C (=0.56) is nearly within the errors of the known value of 0.72+/- 0.1. Furthermore, the age difference derived between a cluster with these values of C and a metallicity of -2.2 is <<1Gyr. Higher metallicity clusters will not have as many faint blue HB stars but for that very reason it will be important to be more complete in our search for these objects in order to derive an accurate value of C, thus requiring equal exposure times for clusters of all metallicities. We will also perform a number of artificial star tests to determine the faint blue star completeness. We have used several independent exposure time estimators to derive appropriate integration times, including the WFPC2 manual, the new WFPC2 exposure time calculator available on the WWW, and a program written by C. Cacciari. The derived S/N values can differ by up to a factor of 2 for a given set of input parameters. We have adopted the most pessimistic estimates. These give a S/N of 5 in 2x1200s in the F555W (V) filter and 3x2500s in the F814W (I) filter for a blue HB star 1 mag below the HB. These exposures also satisfy our requirements for determining V(HB) and (V-I)_g. In addition, note that the turnoff of a 1 Gyr cluster (the suspected age of NGC 205 Hubble V) should be very close to the same magnitude and color as the limit we took for our blue HB observations. Thus, in 4 orbits (1 in F555W and 3 in F814W) of 54--56m duration each, we can obtain the photometric accuracy required for all of our studies. Note that for these calculations we have neglected the background galaxy light, which should not be a factor except for NGC 205 Hubble V and VI, for which the S/N values will be only slightly degraded. Thus, we request 4 orbits per cluster. For each cluster, the first 3 orbits will each consist of ~6m for guide star acquisition plus a single 2800s observation in the F814W filter (for the NGC 205 clusters this will be shortened to 2700s) plus 3m overhead. The last orbit will consist of 5m for guide star acquisition + 2600s CR-SPLIT F555W exposure + 300s CR- SPLIT overhead. Thus, in total we will obtain 2x1300s in F555W and 3x2800s (or 3x2700s) in F814W. We note that this is slightly more than the total exposure time per cluster that we (Sarajedini et al. Cycle 5 grant number 5914) have been granted for very similar observations of globular clusters in M33 which are at the same distance. Experience gleaned from previous shorter observations of M31 clusters indicates that our proposed exposure times are indeed appropriate. Real Time Justification ----------------------- None None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC185-FJJI EXT-CLUSTER,GLOBULAR RA=0H 37M 19.75S +/- 0.1S, 1975. V = 18.4 CLUSTER DEC=+48D 10' 27.1" +/- 1" B-V = 0.79 E(B-V) = 0.19+/-0.03 2 NGC185-FJJII EXT-CLUSTER,GLOBULAR RA=0H 37M 25.15S +/- 0.1S, 1975. V = 19.7 CLUSTER DEC=+48D 10' 02.9" +/- 1" B-V = 0.94 E(B-V) = 0.19+/-0.03 3 NGC185- EXT-CLUSTER,GLOBULAR RA=0H 37M 40.72S +/- 0.1S, 1975. V = 16.8 FJJIII CLUSTER DEC=+48D 11' 44.2" +/- 1" B-V = 0.69 E(B-V) = 0.19+/-0.03 4 NGC185- EXT-CLUSTER,GLOBULAR RA=0H 37M 49.78S +/- 0.1S, 1975. V = 16.7 FJJIV+FJJV CLUSTER DEC=+48D 14' 43.6" +/- 1" B-V = 0.71 E(B-V) = 0.19+/-0.03 5 NGC205-HI EXT-CLUSTER,GLOBULAR RA=0H 40M 30.7S +/- 0.25S, J2000 V = 17.0 CLUSTER DEC=+41D 36' 57.0" +/- 1.7" B-V = 0.54 E(B-V) = 0.04+/-0.03 6 NGC205-HII EXT-CLUSTER,GLOBULAR RA=0H 40M 31.85S +/- 0.25S, J2000 V = 16.7 CLUSTER DEC=+41D 39' 19.0" +/- 1.7" B-V = 0.64 E(B-V) = 0.04+/-0.03 7 NGC205-HV EXT-CLUSTER,GLOBULAR RA=0H 40M 20.49S +/- 0.25S, J2000 V = 16.7 CLUSTER DEC=+41D 40' 49.4" +/- 1.7" B-V = 0.57 E(B-V) = 0.04+/-0.03 8 NGC205-HVI EXT-CLUSTER,GLOBULAR RA=0H 40M 26.22S +/- 0.25S, J2000 V = 17.9 CLUSTER DEC=+41D 42' 05.3" +/- 1.7" B-V = 0.72 E(B-V) = 0.04+/-0.03 9 NGC205-HVII EXT-CLUSTER,GLOBULAR RA=0H 40M 26.62S +/- 0.25S, J2000 V = 18.0 CLUSTER DEC=+41D 42' 53.3" +/- 1.7" B-V = 0.76 E(B-V) = 0.04+/-0.03 10 NGC205-HVIII EXT-CLUSTER,GLOBULAR RA=0H 39M 55.32S +/- 0.25S, J2000 V = 16.7 CLUSTER DEC=+41D 47' 45.7" +/- 1.7" B-V = 0.68 E(B-V) = 0.04+/-0.03 6699( 10) - 11/11/96 10:00 - [ 2] Visit: 01 Visit Requirements: ORIENT 200D TO 30D 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 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC185-FJJI WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 3] Visit: 02 Visit Requirements: ORIENT 10D TO 205D 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 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S I ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S I ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S I ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC185-FJJI WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S I ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 4] Visit: 03 Visit Requirements: ORIENT 250D TO 270D 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 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S II ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S II ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S II ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC185-FJJI WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S II ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 5] Visit: 04 Visit Requirements: ORIENT 250D TO 5D 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 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S V+FJJV ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S V+FJJV ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC185-FJJI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2800 S V+FJJV ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC185-FJJI WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S V+FJJV ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 6] Visit: 05 Visit Requirements: ORIENT 0D TO 180D 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 NGC205-HI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC205-HI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC205-HI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC205-HI WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 7] Visit: 06 Visit Requirements: ORIENT 70D TO 240D 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 NGC205-HII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC205-HII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC205-HII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC205-HII WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 8] Visit: 07 Visit Requirements: ORIENT 230D TO 345D 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 NGC205-HV WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC205-HV WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC205-HV WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC205-HV WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 9] Visit: 08 Visit Requirements: ORIENT 75D TO 180D 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 NGC205-HVI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC205-HVI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC205-HVI WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC205-HVI WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 10] Visit: 09 Visit Requirements: ORIENT 315D TO 100D 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 NGC205-HVII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC205-HVII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC205-HVII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC205-HVII WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 11] Visit: 10 Visit Requirements: ORIENT 0D TO 135D 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 NGC205-HVII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S I ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC205-HVII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S I ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC205-HVII WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 2700 S I ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC205-HVII WFPC2 IMAGE PC1-FIX F555W CR-TOLERANCE=0.0 1 2600 S I ------------------------------------------------------------------------------------------------------------------------------------ 6699( 10) - 11/11/96 10:00 - [ 12] Summary Form for Proposal 6699 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO CR-TOLERANCE=0.0 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 200D TO 30D ORIENT 10D TO 205D ORIENT 250D TO 270D ORIENT 250D TO 5D ORIENT 0D TO 180D ORIENT 70D TO 240D ORIENT 230D TO 345D ORIENT 75D TO 180D ORIENT 315D TO 100D ORIENT 0D TO 135D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC185-FJJI NGC185-FJJII NGC185-FJJIII NGC185-FJJIV+FJJV NGC205-HI NGC205-HII NGC205-HV NGC205-HVI NGC205-HVII NGC205-HVIII ------------------------------------------------------------------------------------------------------------------------------------