5962( 10) - 04/08/96 11:29 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5962 Version: 10 Check-in Date: 08-Apr-1996 11:26:51 1.Proposal Title: Young Globular Clusters in Merging Galaxies: Part 3 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Galaxies & Clusters GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Brad Whitmore Space Telescope Science Institute CoI: Francois Schweizer Carnegie Inst. of Washington - DTM N CoI: Michael Fall Space Telescope Science Institute N CoI: Claus Leitherer Space Telescope Science Institute N CoI: Bryan Miller DTM/STScI N ------------------------------------------------------------------------------------ 6. Abstract Cycle 2 HST observations by our team resulted in the discovery of 40 blue pointlike objects in NGC 7252 (Whitmore et al. 1993) and over 700 similar objects in NGC 4038/4039 (Whitmore & Schweizer 1994). These objects have the luminosities, colors, and radii of young globular clusters and must have formed during the mergers. Because of their proximity and early stage of merging, NGC 4038/4039 (``The Antennae'') is an ideal laboratory to study cluster formation in mergers. Here we propose to follow up the exploratory Cycle 2 observations with a solid combination of deep UBVI photometry, H Alpha imaging, and UV spectroscopy. Our primary goals are to (1) determine the luminosity function (LF) to 3.5 mag fainter than before to see whether it continues to rise like a power law or turns over and forms a Gaussian- like distribution similar to the classical LF of globular clusters, (2) age date the clusters (carefully correcting for reddening) and study their age distribution, and (3) determine the structural properties of the clusters (e.g., radius, central surface brightness, concentration, and ellipticity). These observations should allow us to better assess whether the ultraluminous star clusters observed in recent mergers may evolve to become typical globular clusters. The young clusters' small radii and principal emission in the UV require both the high resolution and improved UV capability of the repaired Space Telescope. ------------------------------------------------------------------------------------ 5962( 10) - 04/08/96 11:29 - [ 2] Observations Description ------------------------ For visit #1, the WFPC2 will be used with filters F336W (``U''; 2X 1000 s + 1100 s + 2 X 1200s), F439W (``B''; 4 X 1000 s, 2 X 60 s), F555W (``V''; 4 X 1100 s, 2 X 60 s), and F814W (``I''; 4 X 500 s, 2 X60 s) to observe the merging galaxies NGC 4038/4039. The short exposures are to guarantee unsaturated images of the brightest clusters. The exposures will be taken at 2 different positions separated by 0.25" in both X and Y. This corresponds to 5.5 PC pixels and 2.5 WF pixels. The subpixel dithering will allow us to obtain better spatial resolution from the undersampled images, while the total of 4 exposures will provide very good cosmic ray removal, and the offset will allow us to remove hot pixels. The position is centered on object # 345 from Whitmore et al., AJ, March 1995, based on WFPC1 observations. The orientation is arranged to fit both NGC 4038 and NGC 4039 into the WF. Visit #2 should be taken at the same orientation as visit 1, and within 30 days. This visit takes short images (2 X 30s in F555W) of a nearby star to aid in the analysis, using the same offsets as visit 1. An H-Alpha image of NGC 4038/4039 will also be taken (F658N; 2 X 900 s + 1000 s + 1100 s), with the normal dithering. The velocities range from 1450 to 1700 km s^-1, whence H-Alpha will be redshifted into the interval 6594- -6600 Angstrom and will be nicely covered by the F658N filter (peak at 6592 Angstrom, range 6572--6610 Angstrom). A combination of the V and I images will be used to subtract the continuum. The S/N for a typical cluster in NGC 4038/4039 should be about 10, based on ground-based estimates of the H-Alpha flux (Keel et al. 1985, AJ, 90, 708; Amram et al. 1992, A&A, 266, 106), and a comparison with our Cycle 4 H-Alpha observations of NGC 4536. For visit # 3, the FOS/BL will be used with the G160L, and the GHRS will be used with the G140L grating and two different wavelength settings (1300 A and 1500 A) to obtain spectra of three of the brightest clusters in NGC 4038/4039. The FOS will be used for the acquisition, using a 2 stage peakup to center object 405 in the 1" aperture. It is possible that we will use an ACQ/BIN for the acquisition, depending on the results of the WFPC2 observations. After the FOS ACCUM observation, and an ACQ observation to obtain an image of the field we actually centered on, the telescope will be offset to the 2.0" aperture of the GHRS. The subsequent clusters will be acquired using a blind offset. WAVE observations are interspersed to determine accurate wavelength calibrations. At present, we plan to observe the clusters 405, 455, and 442. However, we may choose to change one or more of these if the H-Alpha images indicates that any of these are not very young clusters. Hence, visit 2 has been put ON HOLD, pending the H-Alpha observations in visit 2. NOTE ADDED March 18, 1996. The original visit 3 has now been split into 2 parts, visit 3 = FOS (acq) and GHRS observations of cluster 405 and 442, and visit 4 = FOC observations of regions T and G. Real Time Justification ----------------------- Not applicable Not applicable. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 5962( 10) - 04/08/96 11:29 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: STScI Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5962( 10) - 04/08/96 11:29 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4038 Galaxy, RA=12H 01M 50.421S +/- 0.01S, 2000 V=1500 V = 10 DEC=-18D 52' 17.84" +/- 0.01" Comments: Object # 345 from Whitmore et al. AJ, 000. All coordinates from WFPC1 observations. 5 NGC4038- Star, RA=12H 01M 51.606S +/- 0.01S, 2000 V = 16.7 STAR6 DEC=-18D 51' 34.68" +/- 0.01" Comments: Star # 6 from Whitmore et al. AJ, 000. 6 NGC4038-405- Ext-Cluster,Open RA=12H 01M 50.421S +/- 0.05S, 2000 V=1500 F-CONT(5500)=1e-15 UPDATED Cluster,Emission Line DEC=-18D 52' 11.468" +/- 0.5", Nebula PLATE-ID=04UV Comments: Updated target based on early acquisition. 7 NGC4038-442- Galaxy, RA=12H 01M 52.973S +/- 0.05S, 2000 V=1500 F-CONT(5500)=1e-15 UPDATED DEC=-18D 52' 8.37" +/- 0.5", PLATE-ID=04UV Comments: Updated target based on early acquisition. 8 NGC4038-T Star, RA=12H 01M 50.437S +/- 0.01S, 2000 V = 16.9 DEC=-18D 52' 19.23" +/- 0.01", PLATE-ID=04UV Comments: Updated target based on early acquisition. 9 NGC4038-G Star, RA=12H 01M 51.294S +/- 0.01S, 2000 V = 17.3 DEC=-18D 51' 43.449" +/- 0.01", PLATE-ID=04UV Comments: Updated target based on early acquisition. 5962( 10) - 04/08/96 11:29 - [ 5] Visit: 01 Visit Requirements: ORIENTation 275D TO 295D 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 NGC4038 WFPC2 IMAGE PC1 F336W CR-SPLIT=NO 1 1000S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4038 WFPC2 IMAGE PC1 F336W CR-SPLIT=NO 1 1100S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4038 WFPC2 IMAGE PC1 F439W CR-SPLIT=NO 2 1000S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC4038 WFPC2 IMAGE PC1 F439W 1 60S ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC4038 WFPC2 IMAGE PC1 F814W 1 60S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC4038 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO 2 1100S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC4038 WFPC2 IMAGE PC1 F555W 1 60S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC4038 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 500S ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC4038 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 500S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC4038 WFPC2 IMAGE PC1 F439W CR-SPLIT=NO 2 1000S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC4038 WFPC2 IMAGE PC1 F439W 1 60S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC4038 WFPC2 IMAGE PC1 F814W 1 60S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC4038 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO 2 1100S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC4038 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO 1 60S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC4038 WFPC2 IMAGE PC1 F336W CR-SPLIT=NO 2 1200S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 5962( 10) - 04/08/96 11:29 - [ 6] Visit: 02 Visit Requirements: SAME ORIENTation AS 1 GROUP 1-2 WITHIN 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 NGC4038 WFPC2 IMAGE PC1 F658N CR-SPLIT=NO 1 1000S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4038 WFPC2 IMAGE PC1 F658N CR-SPLIT=NO 1 1100S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4038 WFPC2 IMAGE PC1 F658N CR-SPLIT=NO 1 900S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC4038 WFPC2 IMAGE PC1 F658N CR-SPLIT=NO 1 800S POS TARG +0.25, +0.25 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC4038- WFPC2 IMAGE PC1 F555W 1 30S STAR6 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC4038- WFPC2 IMAGE PC1 F555W 1 30S POS TARG +0.25, +0.25 STAR6 ------------------------------------------------------------------------------------------------------------------------------------ 5962( 10) - 04/08/96 11:29 - [ 7] Visit: 03 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 NGC4038-405 FOS/BL ACQ/PEA 4.3 MIRROR SCAN-STEP- 1 3S ONBOARD ACQ FOR 2 -UPDATED K Y=1.23,SEARCH- SIZE-X=1,SEARCH -SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4038-405 FOS/BL ACQ/PEA 1.0 MIRROR SCAN-STEP- 1 6S ONBOARD ACQ FOR 3 -UPDATED K X=0.61,SCAN- STEP- Y=0.61,SEARCH- SIZE-X=6,SEARCH Comments: -SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4038-405 FOS/BL ACQ/PEA 0.5 MIRROR SCAN-STEP- 1 10S ONBOARD ACQ FOR 6-8 -UPDATED K X=0.29,SCAN- STEP- Y=0.29,SEARCH- SIZE-X=3,SEARCH Comments: -SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC4038-405 HRS ACCUM 2.0 G140L 1460 1 45M -UPDATED ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC4038-442 HRS ACCUM 2.0 G140L 1460 1 50M -UPDATED ------------------------------------------------------------------------------------------------------------------------------------ 5962( 10) - 04/08/96 11:29 - [ 8] Visit: 04 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 NGC4038-T FOC/96 IMAGE 512X512 F480LP 1 1000S MAX DUR ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4038-G FOC/96 IMAGE 512X512 F480LP 1 1000S MAX DUR ------------------------------------------------------------------------------------------------------------------------------------ 5962( 10) - 04/08/96 11:29 - [ 9] Summary Form for Proposal 5962 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 FOS/BL HRS FOC/96 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO SEARCH-SIZE-Y=3 SEARCH-SIZE-Y=2 SEARCH-SIZE-X=3 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Galaxies & Clusters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENTation 275D TO 295D POS TARG +0.25, +0.25 SAME ORIENTation AS 1 GROUP 1-2 WITHIN 30D ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 6-8 MAX DUR ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W F439W F814W F555W F658N MIRROR G140L F480LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC4038 NGC4038-STAR6 NGC4038-405-UPDATED NGC4038-442-UPDATED NGC4038-T NGC4038-G ------------------------------------------------------------------------------------------------------------------------------------