9409( 3) - 12/26/02 12:52 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9409 Version: 3 Check-in Date: 24-May-2002 12:27:37 1.Proposal Title: The Evolution of Globular Cluster Systems in Merger Remnants ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Paul Goudfrooij Space Telescope Science Institute CoI: Dr. Francois Schweizer Carnegie Observatories N CoI: Dr. Bradley Whitmore Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract Mergers seem to have played a major role in determining the shapes and dynamics of elliptical galaxies. A few galactic mergers still occur and offer valuable clues to past evolutionary processes. Globular clusters formed during mergers are crucial probes for age-dating such events, and help shed light on the process of cluster formation and evolution. With young globulars in ongoing mergers now well studied, we propose to make deep ACS observations of intermediate-age globular clusters in two bona fide ellipticals: NGC 1316 and 3610. These ellipticals have line-strength indices, UBV colors, and fine structure indicative of their being 2 -- 4 Gyr old merger remnants. Past HST+WFPC2 observations have shown that they also possess significant numbers of intermediate-age globulars as part of their bimodal cluster populations. We plan to use the new HST+ACS observations to (1) measure high- accuracy BVI colors for clusters up to ~ 2 -- 3 mag fainter than ever before, (2) use these colors to separate first- and second-generation clusters, and (3) determine the luminosity functions of the two kinds of clusters to 3 -- 4 mag past the peak for old globulars. Deep dithered BVI images form a crucial part of our observing strategy. This program should permit---for the first time---to directly detect the predicted evolution of the cluster luminosity function from a power law for young clusters to the Gaussian distribution typical of old globulars. ------------------------------------------------------------------------------------ 9409( 3) - 12/26/02 12:52 - [ 2] Observations Description ------------------------ The Advanced Camera for Surveys will be used with the three broad-band filters F435W, F555W and F814W for the target galaxies. These three filters provide the best match to the Johnson-Cousins B_J, V_J, I_C system for which the calibration in terms of age and metallicity is well established (e.g., Maraston 1998; Bruzual & Charlot 2000). We choose to use three filters to achieve the best possible selection criteria to discriminate GCs from faint foreground stars and compact background galaxies, i.e., using specific regions in color- color diagrams rather than only in color- magnitude diagrams (see, e.g., Brown et al. 2000). The main goal of the proposed exposures is to reach S/N = 5 in V and I for intermediate-age GCs with a luminosity that is 2 magnitudes fainter than the calculated turnover magnitude of the LF of second-generation GCs for the age of the galaxy in question assumed to be 3 Gyr for NGC 1316 (Goudfrooij etal 2001a), and 4 Gyr for NGC 3610 (Whitmore etal 1997). The calculations were done following the prescriptions of Goudfrooij et al. (2001b; Section 4.3.1). These observations will ensure a proper identification of that turnover, which constitutes the main scientific aim of this proposal. The main purpose of the B- band exposures is to provide the best possible discrimination between the blue and red GC subpopulations down to 2 mag beyond the turnover of the old GCs (by means of the ~50% higher metallicity dependence of B-I relative to V-I). The sub-exposures are to be positioned so as to allow cosmic-ray removal and multi-position dithering. The latter will be performed to allow a better sampling of the PSF through drizzling (needed to get the best estimates of the GC sizes), as well as to enable one to eliminate the spatial gap between the two ACS chips. Real Time Justification ----------------------- We request to have the observations of NGC 3610 conducted during CVZ orbits. This will constitute a very efficient use of HST, and seems to be well possible: Its coordinates (RA ~ 170 degrees, DEC ~+59 degrees) allows a ``Maximum Duration of any single CVZ Opportunity'' of 50 orbits, a ``Total Duration of All CVZ Opportunities'' of 266 orbits, and a total of 7 CVZ opportunities during Cycle 11 according to the CVZ tables available through the Call for Proposals web pages. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9409( 3) - 12/26/02 12:52 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1316 GALAXY, Radio Galaxy, RA=3H 22M 41.71S +/- 0.02S, J2000 V = SURF(V) = 13.4+/-0.2 Interacting Galaxy DEC=-37D 12' 29.4" +/- 0.3", +1760 B-V = 0.93 PLATE-ID=02IW U-B = 0.47 Coordinate Source: HST_IMAGE Comments: Colors from RC3, central surface brightness and center coordinates from Cycle-5 WFPC2 frames. 2 NGC3610 GALAXY, ELLIPTICAL RA=11H 18M 25.166S +/- 0.02S, J2000 V = SURF(V) = 12.1+/-0.1 DEC=58D 47' 10.83" +/- 0.3", +1696 B-V = 0.86+/-0.01 PLATE-ID=01OJ Coordinate Source: HST_IMAGE Comments: Elliptical galaxy (E5) with central disk at PA=133D. Center coordinates and surface brightness from Cycle-4 WFPC2 frames. 9409( 3) - 12/26/02 12:52 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.265 Coordinate_Frame POS-TARG Pattern_Orient 20.67 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.1492 Coordinate_Frame POS-TARG Pattern_Orient 4.38 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9409( 3) - 12/26/02 12:52 - [ 5] Visit: 01 Visit Priority: Visit Requirements: SCHED 80% GROUP 1-2 WITHIN 30 D ORIENT 35D TO 117D ORIENT 123D TO 131D ORIENT 148D TO 169D ORIENT 183D TO 191D ORIENT 213D TO 254D ORIENT 313D TO 321D On Hold Comments: Additional Comments: The reason for the ORIENT ranges is the WFPC2 parallels: The ORIENT ranges will avoid bright stars in the regions that would cause scattered light within the WFPC2. Also avoid ORIENTS +/- 45D within that of NGC 1317 (a nearby spiral galaxy), but pointing WFPC2 at NGC 1317 itself would be fine (cf. last listed ORIENT range). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1316 ACS/WF ACCUM WFC F814W GAIN=1,CR-SPLIT=NO 1 90 S C Comments: Short exp to avoid saturation of nucleus ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC1316 ACS/WF ACCUM WFC F435W GAIN=1,CR-SPLIT=NO 1 620 S C Comments: default position ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC1316 ACS/WF ACCUM WFC F435W GAIN=1,CR-SPLIT=NO 1 620 S PATTERN 2 40 C Comments: 2-point integer line dither ------------------------------------------------------------------------------------------------------------------------------------ 110 NGC1316 ACS/WF ACCUM WFC F814W GAIN=1,CR-SPLIT=NO 1 90 S C Comments: Short exp to avoid saturation of nucleus ------------------------------------------------------------------------------------------------------------------------------------ 120 NGC1316 ACS/WF ACCUM WFC F814W GAIN=1,CR-SPLIT=NO 1 1100 S PATTERN 1 120-121 PAR 121 C with 120 Comments: 2-point line dither, 1 orbit ------------------------------------------------------------------------------------------------------------------------------------ 121 NGC1316 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 700 S IX ------------------------------------------------------------------------------------------------------------------------------------ 210 NGC1316 ACS/WF ACCUM WFC F814W GAIN=1,CR-SPLIT=NO 1 1240 S POS TARG 0.248, 3.001 C PATTERN 1 210-211 PAR 211 WITH 210 Comments: Jumping ~3 arcsec up (chip gap is 2.5 arcsec), then same 2-pt line dither as above. ------------------------------------------------------------------------------------------------------------------------------------ 211 NGC1316 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 800 S IX ------------------------------------------------------------------------------------------------------------------------------------ 9409( 3) - 12/26/02 12:52 - [ 6] Visit: 02 Visit Priority: Visit Requirements: SCHED 80% SAME ORIENT AS 1 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 ------------------------------------------------------------------------------------------------------------------------------------ 310 NGC1316 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 200 S C Comments: Default position; short exp. in F555W ------------------------------------------------------------------------------------------------------------------------------------ 320 NGC1316 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1000 S C Comments: Default position, F555W ------------------------------------------------------------------------------------------------------------------------------------ 330 NGC1316 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1000 S POS TARG 0.116, 0.075 PAR C 331 WITH 330 Comments: F555W, second dither (2 1/3, 1 1/3 pix) ------------------------------------------------------------------------------------------------------------------------------------ 331 NGC1316 WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 700 S IX ------------------------------------------------------------------------------------------------------------------------------------ 410 NGC1316 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 200 S C Comments: Default position; short exp. in F555W ------------------------------------------------------------------------------------------------------------------------------------ 420 NGC1316 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1050 S POS TARG 0.231, 0.150 PAR C 421 WITH 420 Comments: third dither near default position (4 2/3, 2 2/3 pix) ------------------------------------------------------------------------------------------------------------------------------------ 421 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 700 S IX ------------------------------------------------------------------------------------------------------------------------------------ 430 NGC1316 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1050 S POS TARG 0.248, 3.001 PAR C 431 WITH 430 Comments: Jump 3" up across gap; first F555W dither there ------------------------------------------------------------------------------------------------------------------------------------ 431 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 700 S IX ------------------------------------------------------------------------------------------------------------------------------------ 510 NGC1316 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1240 S POS TARG 0.364, 3.076 PAR C 511-512 WITH 510 Comments: Second F555W dither position across gap (2 1/3, 1 1/3 pix from exp 430) ------------------------------------------------------------------------------------------------------------------------------------ 511 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 400 S IX ------------------------------------------------------------------------------------------------------------------------------------ 512 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 400 S IX ------------------------------------------------------------------------------------------------------------------------------------ 9409( 3) - 12/26/02 12:52 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 520 NGC1316 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1240 S POS TARG 0.479, 3.151 PAR C 521-522 WITH 520 Comments: Third F555W dither position across gap (4 2/3, 2 2/3 pix from exp 430) ------------------------------------------------------------------------------------------------------------------------------------ 521 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 400 S IX ------------------------------------------------------------------------------------------------------------------------------------ 522 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 400 S IX ------------------------------------------------------------------------------------------------------------------------------------ 9409( 3) - 12/26/02 12:52 - [ 8] Visit: 03 Visit Priority: Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC3610 ACS/WF ACCUM WFC F814W GAIN=1,CR-SPLIT=NO 1 100 S POS TARG 0, 9.99 C Comments: Default pointing 20" from inter-chip gap ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC3610 ACS/WF ACCUM WFC F435W GAIN=1,CR-SPLIT=NO 1 360 S POS TARG 0, 9.99 C Comments: Default pointing ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC3610 ACS/WF ACCUM WFC F435W GAIN=1,CR-SPLIT=NO 1 360 S POS TARG 0, 9.99 PATTERN C 2 Comments: Default pointing; 2-pt, small integer-pix line dither ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC3610 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1160 S POS TARG 0, 9.99 PATTERN C 1 40-41 PAR 41 WITH 40 Comments: Default pointing; 2-pt line dither; deep F555W data ------------------------------------------------------------------------------------------------------------------------------------ 41 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 900 S IX ------------------------------------------------------------------------------------------------------------------------------------ 110 NGC3610 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1160 S POS TARG -0.124, 10.13 C PATTERN 1 110-111 PAR 111 WITH 110 Comments: 2-point line dither, making 4 dither positions total ------------------------------------------------------------------------------------------------------------------------------------ 111 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 800 S IX ------------------------------------------------------------------------------------------------------------------------------------ 120 NGC3610 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 240 S POS TARG -0.1984, 9.810 C Comments: Short exp. in F555W, at fifth dither position ------------------------------------------------------------------------------------------------------------------------------------ 130 NGC3610 ACS/WF ACCUM WFC F555W GAIN=1,CR-SPLIT=NO 1 1530 S POS TARG -0.1984, 9.810 C PAR 131-132 WITH 130 Comments: long F555W exp at fifth dither position ------------------------------------------------------------------------------------------------------------------------------------ 131 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 500 S IX ------------------------------------------------------------------------------------------------------------------------------------ 132 ANY WFPC2 IMAGE WFALL-F F555W CR-SPLIT=NO 1 700 S IX ------------------------------------------------------------------------------------------------------------------------------------ 9409( 3) - 12/26/02 12:52 - [ 9] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 210 NGC3610 ACS/WF ACCUM WFC F814W GAIN=1,CR-SPLIT=NO 1 1160 S POS TARG -0.1984, 9.810 C PAR 211 WITH 210 Comments: first the same pos. as last exp., now F814W ------------------------------------------------------------------------------------------------------------------------------------ 211 ANY WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 800 S IX ------------------------------------------------------------------------------------------------------------------------------------ 220 NGC3610 ACS/WF ACCUM WFC F814W GAIN=1,CR-SPLIT=NO 1 1200 S POS TARG 0, 9.99 PATTERN C 1 220-222 PAR 221-222 WITH 220 Comments: Default position; 2-point line dither ------------------------------------------------------------------------------------------------------------------------------------ 221 ANY WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 400 S IX ------------------------------------------------------------------------------------------------------------------------------------ 222 ANY WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 230 NGC3610 ACS/WF ACCUM WFC F814W GAIN=1,CR-SPLIT=NO 1 1200 S POS TARG -0.124, 10.13 C PATTERN 1 230-232 PAR 231-232 WITH 230 Comments: 2-pt line dither at different pos., making 5 pos total. ------------------------------------------------------------------------------------------------------------------------------------ 231 ANY WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 400 S IX ------------------------------------------------------------------------------------------------------------------------------------ 232 ANY WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 300 S IX ------------------------------------------------------------------------------------------------------------------------------------ 9409( 3) - 12/26/02 12:52 - [ 10] Summary Form for Proposal 9409 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC WFALL-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters GAIN=1 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SCHED 80% GROUP 1-2 WITHIN 30 D ORIENT 35D TO 117D ORIENT 123D TO 131D ORIENT 148D TO 169D ORIENT 183D TO 191D ORIENT 213D TO 254D ORIENT 313D TO 321D PATTERN 2 40 PATTERN 1 120-121 PAR 121 with 120 POS TARG 0.248, 3.001 PATTERN 1 210-211 PAR 211 WITH 210 SCHED 80% SAME ORIENT AS 1 POS TARG 0.116, 0.075 PAR 331 WITH 330 POS TARG 0.231, 0.150 PAR 421 WITH 420 POS TARG 0.248, 3.001 PAR 431 WITH 430 POS TARG 0.364, 3.076 PAR 511-512 WITH 510 POS TARG 0.479, 3.151 PAR 521-522 WITH 520 CVZ POS TARG 0, 9.99 POS TARG 0, 9.99 PATTERN 2 POS TARG 0, 9.99 PATTERN 1 40-41 PAR 41 WITH 40 POS TARG -0.124, 10.13 PATTERN 1 110-111 PAR 111 WITH 110 POS TARG -0.1984, 9.810 POS TARG -0.1984, 9.810 PAR 131-132 WITH 130 POS TARG -0.1984, 9.810 PAR 211 WITH 210 POS TARG 0, 9.99 PATTERN 1 220-222 PAR 221-222 WITH 220 POS TARG -0.124, 10.13 PATTERN 1 230-232 PAR 231-232 WITH 230 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F435W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1316 ANY NGC3610 ------------------------------------------------------------------------------------------------------------------------------------