6636( 9) - 06/19/96 10:17 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6636 Version: 9 Check-in Date: 19-Jun-1996 10:14:30 1.Proposal Title: The Stellar Population of M32: A Dual Approach ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle STELLAR POPULATIONS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Michael Gregg IGPP CoI: Robert Becker University of California, Davis N ------------------------------------------------------------------------------------ 6. Abstract M32 has been the focus of exhaustive ground-based spectroscopic and photometric studies to determine its stellar content. No consensus has yet emerged on either its mean age or metallicity. M32 is key to understanding stellar populations in early type galaxies and learning how to model the integrated light of more distant systems, regardless of whether or not its stellar population is typical, because it can be observed both as an integrated light system and as resolved stars. This proposal will investigate the questions of age and metallicity of M32 using the unique capabilities of HST to obtain UV spectroscopy of M32. The turnoff region will be modeled from combined HST UV and ground-based optical spectra in a consistent manner to probe the age of the most recent epoch of significant star formation in M32. ------------------------------------------------------------------------------------ 6636( 9) - 06/19/96 10:17 - [ 2] Observations Description ------------------------ Summary: The primary goal is to obtain a near-UV spectrum of the nucleus of M32 using FOS/RD + G270H (2222-3270Angstrom) and aperture 1.0-PAIR-A. A supplementary short exposure spectrum using G400H and the same aperture will also be obtained to facilitate matching the UV spectrum to the ground-based optical spectrum. Acquisition will be a 5-stage peak-UP using G570H which maximizes system throughput and saves integration time over G270H or even G400H. Acquisition: A 5-stage peak-UP will be done using G570H. The red spectral energy distribution and higher efficiency of G570H more than compensates for the time lost to changing grating one additional time. The initial acquisition series will be increased from the standard 1x3 to 2x5 because there remains some uncertainty in the best available position at the 1arcsec level; the 2x5 series insures a much greater chance of successful acquisition and does not impinge on the science exposures. Count rate estimates for the acquisition exposures have come from the Cycle 5 RPS2 file of van der Marels et al. (prop 5847) and from the FOS ACQ Simulator Software of van der Marels available over the Web. Science Exposures: after acquisition, the grating is changed to G400H for a 5 minute exposure through 1.0-PAIR-A (upper). Although this is a paired aperture, no chopping should be done (STEP- PATT=SINGLE). Because this spectrum will be obtained through the same aperture as the UV spectrum, it will give continuous spectral coverage out to 4700Angstroms of the identical region. This will allow direct scaling of the UV spectrum to the higher resolution, higher S/N ground-based spectrum of M32 which has been obtained through a somewhat larger aperture by the PI. The G400H spectrum is expected to be S/N about 20-25 or better at its short wavelength end. Next, the near UV spectrum of the nucleus of M32 will be obtained using G270H and the UPPER aperture of 1.0-PAIR. The goal is to reach S/N of 25 or better over the entire range of grating G270H, 2200-3270Angstrom. Only the UPPER aperture will be used as it has better flat-fielding characteristics. CCD surface photometry of M32 (Lauer et al. 1992) shows that m_V=12.99 in the 0arcs86 square aperture (prop 5847; FOS ACQ Simulator). Accurate estimates of F_Lambda at all UV wavelengths follow directly from the IUE data, assuming no color gradients. The formulae in the FOS Instrument Handbook predict count rates of 0.123 cts/s/diode at the blue limit of G270H, 2200Angstrom, rising to >~1.5 cts/s/diode at 3000A. Taking into account dark current, S/N = 20-25 can be obtained in the remaining 2+ orbits at the blue limit; redward, S/N = 50 will be reached. Parallel observations: Once the nucleus of M32 is acquired, parallel observations using WFPC2 will be carried out to image a region of the disk of NGC224 (M31). Exposures with F555W, F450W, and F814W will be done during the second, third, and fourth orbits, respectively. Each will be CR- SPLIT by 2 only, for adequate cosmic ray removal will interrupting the FOS exposure just once each orbit for WFPC2 readout. In order to sample a region of the disk which has comparable surface brightness to the M31 disk which underlies M32, orientation restrictions of 85D TO 105D OR 255D TO 275D are requested. This leaves roughly 6-8 weeks scheduling window. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6636( 9) - 06/19/96 10:17 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6636( 9) - 06/19/96 10:17 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC221 GALAXY, ELLIPTICAL RA=0H 42M 41.824S +/- 0.075S, J2000 V = -202 B-V = 0.95 DEC=40D 51' 53.91" +/- 0.67", E(B-V) = 0.10 PLATE-ID=0738 V = 11.23+/-0.2 SIZE=4.16 V = 12.99+/-0.2 SIZE=0.97 V = 15.09+/-0.2 SIZE=0.24 Comments: Coordinates have been adopted from Cycle 5 proposal (5847) of van der Marels et al. whose acquisition was successful. These coordinates are in the Guide Star Reference Frame. 6636( 9) - 06/19/96 10:17 - [ 5] TARGET LIST c)Generic Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria | Flux data No | Name | Description | | ------------------------------------------------------------------------------------------------------------------------------------ NGC224-DISK GALAXY, SPIRAL RA=0H 42M 41.824S +/- 5M,DEC=40D V = 25.5 51' 53.91" +/- 15' Comments: P <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< arallel WFPC2 target: star field in disk of NGC224; V magnitude is rough estimate of horizontal branch magnitude. ------------------------------------------------------------------------------------------------------------------------------------ 6636( 9) - 06/19/96 10:17 - [ 6] Visit: 01 Visit Requirements: ORIENT 85D TO 105D On Hold Comments: Additional Comments: In order to maintain relative wavelength scale during visit, please do not move optical elements during this program. The ORIENTation restriction is to ensure that the WFPC2 parallel exposures are obtained in regions where the disk of NGC224 is comparable surface brightness to the location of M32. Either range is acceptable, but the 85D to 105D is slightly preferred, even though this results in later scheduling. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 110 NGC221 FOS/RD ACQ/PEA 4.3 G570H SCAN-STEP-X = 3.0,SCAN-STEP-Y = 1 2.0 S ONBOARD ACQ FOR 120 NO K 1.23,SEARCH-SIZE-X = 2, SPLIT SEARCH-SIZE-Y = 5,TYPE = UP Comments: M32 nucleus falls in this 2*5 search pattern with very high probability. Exposure time yields 40000 counts on the nucleus. Total V mag. through 4.3 aperture is 11.23, much fainter than G570H red side brightness limit. ------------------------------------------------------------------------------------------------------------------------------------ 120 NGC221 FOS/RD ACQ/PEA 1.0-PAI G570H SCAN-STEP-X = 0.61,SCAN-STEP-Y = 1 2.0 S ONBOARD ACQ FOR 130 NO K R-A 0.61,SEARCH-SIZE-X = 6, SPLIT SEARCH-SIZE-Y = 2,TYPE = UP Comments: Exposure time yields 20000 counts on the nucleus. This is a paired aperture, but NO sky-chopping should be used. ------------------------------------------------------------------------------------------------------------------------------------ 130 NGC221 FOS/RD ACQ/PEA 0.5-PAI G570H SCAN-STEP-X = 0.2867,SCAN-STEP-Y 1 5.3 S ONBOARD ACQ FOR 140 NO K R = 0.2867,SEARCH-SIZE-X = 3, SPLIT SEARCH-SIZE-Y = 3,TYPE = UP Comments: Exposure time yields >10000 counts on the nucleus. Exposures 10,20,30 must be completed in first orbit of visit. This is a paired aperture, but NO sky-chopping should be used. ------------------------------------------------------------------------------------------------------------------------------------ 140 NGC221 FOS/RD ACQ/PEA 0.25-PA G570H SCAN-STEP-X = 0.17,SCAN-STEP-Y = 1 7.5 S ONBOARD ACQ FOR 150 NO K IR 0.17,SEARCH-SIZE-X = 3, SPLIT SEARCH-SIZE-Y = 3,TYPE = UP Comments: Exposure time yields nearly 10000 counts on the nucleus. This is a paired aperture, but NO sky-chopping should be used. ------------------------------------------------------------------------------------------------------------------------------------ 150 NGC221 FOS/RD ACQ/PEA 0.25-PA G570H SCAN-STEP-X = 0.052,SCAN-STEP-Y = 1 8.0 S ONBOARD ACQ FOR 210 NO K IR 0.052,SEARCH-SIZE-X = 3, SPLIT SEARCH-SIZE-Y = 3,TYPE = UP Comments: Exposure time yields roughly 10000 counts on the nucleus. This is a paired aperture, but NO sky-chopping should be used. ------------------------------------------------------------------------------------------------------------------------------------ 210 NGC221 FOS/RD ACCUM 1.0-PAI G400H STEP-PATT = SINGLE 1 375 S R-A Comments: Orbit 2; red exposure for tie-in to optical ------------------------------------------------------------------------------------------------------------------------------------ 6636( 9) - 06/19/96 10:17 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 215 NGC224-DISK WFPC2 IMAGE WFALL F555W CR-SPLIT=NO 1 600 S PAR WITH 210 Comments: Orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 220 NGC221 FOS/RD ACCUM 1.0-PAI G270H STEP-PATT = SINGLE 1 961 S R-A Comments: Orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 225 NGC224-DISK WFPC2 IMAGE WFALL F555W CR-SPLIT=NO 1 1200 S PAR WITH 220 Comments: Orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 310 NGC221 FOS/RD ACCUM 1.0-PAI G270H STEP-PATT = SINGLE 1 1043 S R-A Comments: Orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 315 NGC224-DISK WFPC2 IMAGE WFALL F450W CR-SPLIT=NO 1 1300 S PAR WITH 310 Comments: Orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 320 NGC221 FOS/RD ACCUM 1.0-PAI G270H STEP-PATT = SINGLE 1 1043 S R-A Comments: Orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 325 NGC224-DISK WFPC2 IMAGE WFALL F450W CR-SPLIT=NO 1 1200 S PAR WITH 320 Comments: Orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 410 NGC221 FOS/RD ACCUM 1.0-PAI G270H STEP-PATT = SINGLE 1 1043 S R-A Comments: Orbit 4 ------------------------------------------------------------------------------------------------------------------------------------ 415 NGC224-DISK WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 1 1300 S PAR WITH 410 Comments: Orbit 4 ------------------------------------------------------------------------------------------------------------------------------------ 420 NGC221 FOS/RD ACCUM 1.0-PAI G270H STEP-PATT = SINGLE 1 1043 S R-A Comments: Orbit 4 ------------------------------------------------------------------------------------------------------------------------------------ 425 NGC224-DISK WFPC2 IMAGE WFALL F814W CR-SPLIT=NO 1 1200 S PAR WITH 420 Comments: Orbit 4 ------------------------------------------------------------------------------------------------------------------------------------ 6636( 9) - 06/19/96 10:17 - [ 8] Summary Form for Proposal 6636 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-X = 3.0 SCAN-STEP-Y = 1.23 SEARCH-SIZE-X = 2 SEARCH-SIZE-Y = 5 TYPE = UP SEARCH-SIZE-Y = 2 SEARCH-SIZE-Y = 3 SEARCH-SIZE-X = 3 SCAN-STEP-Y = 0.052 STEP-PATT = SINGLE CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 85D TO 105D ONBOARD ACQ FOR 120 NO SPLIT ONBOARD ACQ FOR 130 NO SPLIT ONBOARD ACQ FOR 140 NO SPLIT ONBOARD ACQ FOR 150 NO SPLIT ONBOARD ACQ FOR 210 NO SPLIT PAR WITH 210 PAR WITH 220 PAR WITH 310 PAR WITH 320 PAR WITH 410 PAR WITH 420 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G570H G400H F555W G270H F450W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC221 NGC224-DISK ------------------------------------------------------------------------------------------------------------------------------------