Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 3647c Report Date: 09-May-96:18:46 Version: ********** Check-in Date: ********** 1.Proposal Title: THE STAR-FORMING HISTORIES OF ELLIPTICAL GALAXIES ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO Sub Category NEARBY GALAXIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Henry C. Ferguson UNIVERSITY OF CAMBRIDGE, INS ENGLAND 0223-337548 ------------------------------------------------------------------------------------ 7. Abstract We propose to obtain high S/N UV spectra to investigate the history of star formation in elliptical galaxies. These observations will provide an order of magnitude improvement in spectral signal-to-noise over that previously attainable with IUE. The data will also supplement and complement the limited set of elliptical -galaxy observations made in December 1990 with Astro-1. The HST spectra promise additional important constraints on the metallicity distribution and ages of the hot stellar component in these galaxies. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 15.00 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 3647c PI: Henry C. Ferguson Proposal Title: THE STAR-FORMING HISTORIES OF ELLIPTICAL GALAXIES ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Henry C. Ferguson UNIVERSITY OF CAMBRIDGE, ENGLAND X INSTITUTE OF ASTRONOMY Bradley C. Whitmore SPACE TELESCOPE SCIENCE USA INSTITUTE Kirk D. Borne SPACE TELESCOPE SCIENCE USA INSTITUTE Ralph C. Bohlin SPACE TELESCOPE SCIENCE USA INSTITUTE Arthur F. Davidsen THE JOHNS HOPKINS UNIVERSITY USA William Sparks SPACE TELESCOPE SCIENCE USA INSTITUTE Robert C. Thomson UNIVERSITY OF CAMBRIDGE, ENGLAND X INSTITUTE OF ASTRONOMY Stephen Zepf PHYSICS DEPTARTMENT, UNIVERSITY ENGLAND X OF DURHAM ------------------------------------------------------------------------------------ 3. Description of proposed observations. The FOS will be used with the G270H grating and 1" X 1" aperture to obtain spectra in the region 2200 - 3300 A (i.e., dominated by intermediate age stars). Absorption lines of interest lie at 2650, 2850, and 3050 A. The signal-to-noise ratios will range from 7 - 10 per A when possible. The FOS will also be used with the G190H grating to cover the region 1600 - 2300 A, where IUE spectra of ellipticals show considerable variety, and where the 2200 A interstellar absorption feature may be evident. Here is a summary of the proposed observations. The fluxes either estimated or measured in the IUE aperture are listed first, followed by exposure times computed to give S/N of 7-10 per A for spectra within a 3" diameter circle for imaging. NGC 1399 NGC 3610 F(1400) 11.0 e-15 1.7 e-15 F(2700) 4.4 e-15 5.6 e-15 FOS G130H 180M 180M FOS G190H 90M 120M FOS G270H 60M 60M NOTE: STScI HAS MODIFIED THIS PROPOSAL WITH THE ADDITION OF NEW ACQ/PEAKs BEFORE EACH FOS/BL SEGMENT DUE TO NEW SIDE-SWITCHING RULES. (THE SIDE SWITCH WAS ALLOWABLE AS ORIGINALLY SUBMITTED AT THE TIME OF SUBMISSION.) ALSO, SEQ NO GAP SPECIAL REQUIREMENTS HAVE BEEN RELAXED TO SEQ WITHIN 36 HOURS BY STSCI SINCE THE SEQUENCES ARE TOO LONG TO FIT WITHIN NON-SAA IMPACTED ORBITS. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The UV spectra will provide the ability to: 1) constrain the number of massive O and B stars from strengths of the CIV and Si absorption features 2) determine the number of intermediate-age stars, both from the level and shape of the continuum, and from various absorption lines 3) constrain the metallicity of the near-UV component from the strengths of absorption features such as the iron-line blends near 2400 A, 2600 A and 3000 A, the MgII doublet at 2800 A, and the MgI line at 2852 A, and 4) discriminate between the different theories for the origin of the far-UV flux (i.e., star formation, PAGB stars, hot horizontal branch stars, or accreting white dwarfs). Observations of NGC 1399 have also been made using the Hopkins Ultraviolet Telescope (Ferguson et al. 1991) and with IUE. Page 3 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. S/N REQUIREMENTS: Spectra: S/N = 7 - 10 per Angstrom. This will be sufficient for detailed spectral synthesis. Minimum and maximum exposure times: 1200 s (20 m) is used as the minimum, even if the resulting S/N is greater than required; since the overhead begins to dominate anyway. For the maximum we have used 14400 s (4 hr). Assumptions: To ensure that we reach our desired S/N, we have made fairly conservative assumptions about the UV flux from the targets with the spectrograph apertures. Specifically, we have assumed that the UV profile follows the optical profile, and have used optical surface photometry (from the literature and from our own unpublished data) to compute the ratio of the flux in the FOS aperture to the flux in the IUE aperture. This is a conservative assumption because the optical profiles are affected by seeing, and because the UV is likely to be more centrally peaked. However, this is countered by the fact that some of the light is lost from the aperture due to the HST spherical abberation. For NGC3610 we have assumed a UV upturn similar to that in NGC3379. GENERAL DEFINITIONS: s = count rate per Angstrom (A) per second source through = fraction of the IUE flux expected in the smaller HST apertures F = flux in ergs / cm **2 / s / A eff = efficiency of grating (or filter) and detector wave = wavelength d = dark count t = exposure time EXAMPLE OF TYPICAL CALCULATION: FOS formula: (based on eq. 1, p. 56 of handbook, but per A instead of diode, and correcting for source throughput) s = 2.28 e12 X F X wave X eff X source through if> F = 1.0 e-15 wave = 2700 A eff = 0.052 (p. 10 of handbook) source through = 0.045 d = 0.0027 per diode, or .0013 per A s = 0.0144 ct/sec/A S/N = [ s * t * (s/d) / ((s/d) + 1) ] ** 1/2 = 7.9 per A (for exp. time =4800 s) ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Not applicable. Page 4 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. Data will be reduced using the STSDAS standard packages in STSDAS. A spectral synthesis program being used for analysis of the HUT data will be used to analyze the HST spectra. This program uses the "isochrone synthesis" technique of Charlot and Bruzual (1990), and incorporates state-of-the art evolutionary tracks for massive stars from Maeder and Meynet (1988) and PAGB tracks from Schoenberner (1981, 1983). Model spectra are constructed using either real IUE stellar spectra or Kurucz model atmospheres. The program is entirely table driven, and several technical improvements in the input data are expected by the time the HST observations are available. In particular, evolutionary tracks using new opacities are likely to be available, as are tracks for metal-rich extreme HB stars (Pinsonneault, private communication). Kurucz (1991) models with a resolution of 10 A covering a wide range of gravities, temperatures, and abundances will also be available, allowing us to overcome the limitation of empirical stellar libraries for stars with near-solar abundances. In fitting model spectra to the data, we will make extensive use of the nonlinear least- squares fitting rogram 'specfit' now running under IRAF at Johns Hopkins and at Cambridge. A rough division of responsibilities is as follows: HF is responsible for coordinating the overall effort, performing standard reductions of ,spectra, and developing synthesis models for each galaxy; BW will perform spectral reconstructions based on latest STScI expertise and search HST archives for relevant ancillary information (e.g., UV spectra of stars in order to build up a library for spectral synthesis, UV spectra of other ellipticals for comparison sample, etc.); RB will provide expertise on optimizing the observations with the FOS, and will provide the IUE stellar spectral library and relevant FOS spectra; KB will modify his existing N-body code to include gasseous dissipation and star formation and will use the code to help interpret data, especially for the ellipticals that show evidence of recent interactions; SZ will provide ground- based data in support of the HST observations; AFD will provide expertise on FOS and HUT. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. The GASP system will be used to determine better target coordinates during phase II. ------------------------------------------------------------------------------------ 9. Description of previous HST work. Bohlin and Davidsen are on the FOS GTO team; Sparks is affiliated with the FOC GTO team. Observations for these teams are listed in documents readily available. Observations possibly relevant to this proposal include: 1034 - "M87'S JET, NUCLEUS, AND HOT CORONA (FOS NO. 12): CYCLE 0 OBSERVATIONS" 1038 - "IMAGING AND SPECTROPHOTOMETRY OF NUCLEAR ACTIVITY IN LINERS 1041 - "THE NUCLEUS OF NORMAL AND STARBURST GALAXIES (FOS 20): CYCLE 0 1044 - "STELLAR AND GAS DYNAMICS IN NORMAL GALAXIES (FOS 24): CYCLE 0 3105 - "UV IMAGING OF M31-GROUP GALAXIES " 2266 - "POST ASYMPTOTIC GIANT BRANCH EVOLUTION IN THE MAGELLANIC CLOUDS. " ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). HF is funded by an SERC rolling grant for observational astronomy, through September 1992, with the possibility of extension to 1993. Computing facilities at Cambridge include four SUN-4 computers dedicated to HST projects, with a total of 4 Gigabytes of disk storage, and an exabyte cartridge tape system for off-line storage. Each SUN has at least 24 Mb of core memory and a i860 array processors have recently been installed to speed up image deconvolutions. An extensive suite of software is installed on the SUNs, including IRAF, STSDAS, FIGARO, VISTA, and MEMSYS5. These systems are maintained by an in-house support staff funded by STARLINK. Resources at STScI are, of course, designed to support reduction Analysis of HST data. The budget being submitted with this proposal will provide the additional support necessary. Page 5 ------------------------------------------------------------------------------------ 11. Address Information Name: HENRY C. FERGUSON Category: PI Institution: UNIVERSITY OF CAMBRIDGE, INSTITUT Address: THE OBSERVATORIES, MADINGLEY ROAD City: CAMBRIDGE State: Zip Code: CB3 0HA Country: ENGLAND Telephone: (0223) 337548 Telex (or e-mail): 817297 ASTRON G ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 3647c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1399 E, 303, 309 RA = 03H 38M 29.0S +/- 0.1S, 2000 V = 1447 1 V = 9.56 ESO358-45 DEC = -35D 27' 00" +/- 2" 2 B-V = 0.99 PGC13418 3 E(B-V) = 0.0 4 V = 15.90 5 F-CONT(1500) = 3.0 E-15 6 F-CONT(1900) = 4.7 E-16 7 F-CONT(2700) = 1.1 E-16 Comments: FLUXES ARE ESTIMATED USING IUE AND OPTICAL DATA APJS 64,601; AJ 98,538 APJ 328, 440. FLUX1 = V TOTAL. FLUXES 4-7 ARE ESTIMATES IN A 1" SQUARE APERTURE, OBTAINED BY SCALING IUE DATA BY OPTICAL SURFACE BRIGHTNESS PROFILE. 2700A FLUX IS FROM NGC4649. UNCERTAINTIES ARE PROBABLY ~50%. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3610 E, 303, 320 RA = 11H 18M 25.2S +/- 0.1S, 2000 V = 1787 1 V = 10.90 UGC6319 DEC = +58D 47' 10.4" +/- 1" 2 B-V = 0.82 PGC34566 3 E(B-V) = 0.0 4 V = 15.82 5 F-CONT(1500) = 1.3 E-16 6 F-CONT(1900) = 1.3 E-16 7 F-CONT(2700) = 2.3 E-16 Comments: FLUXES ARE ESTIMATED USING IUE AND OPTICAL DATA APJS 64,601; R BAND CCD IMAGE; APJ 328, 440; LONGO AND DEVAUC. TEXAS MONOGRAPH. FLUX1 = V TOTAL; FLUXES 4 -7 ARE ESTIMATES IN 1" SQ. APERTURE, FROM SCALING IUE DATA BY OPTICAL SB PROF. 1500A AND 1900A ARE FROM NGC4742; 2700A FROM NGC2681 (X .787). UNCERTAIN BY FACTORS OF 2 (2700A) TO 10 (1500A) ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3647c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1399 FOS/RD ACQ/ 1.0 MIRROR TYPE=UP 1 35S 20 4 1 ONBOARD ACQ FOR 2- PEAK SCAN-STEP=0.7 3 SEARCH-SIZE=4 SEQ 1-4 WITHIN 36 H CYCLE 2 / 1-8 Comments: WANT TO MAXIMIZE S/N, SO DO A COARSE PEAKUP TO GET WITHIN ABOUT 0.35" OF BRIGHTEST SPOT. ALTHOUGH NUCLEUS PER SE IS NOT THE TARGET, WE WISH ALL OBS FOR BOTH SIDES TO BE TAKEN WITH SAME POINTING. STSCI SAYS NOT POSSIBLE. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC1399 FOS/RD ACCUM 1.0 G190H 1 5284.2S 11 6 1 Comments: S/N IS MEAN PER ANGSTROM. IT MIGHT MAKE SENSE TO SCHEDULE THE NGC1399 OBSERVATIONS AFTER THOSE FOR PROPOSAL 3728 (FOC IMAGING OBSERVATIONS.) THIS IS NOT A REQUIREMENT, THOUGH. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC1399 FOS/RD ACCUM 1.0 G270H 1 3542.4S 15 7 1 Comments: S/N IS MEAN PER ANGSTROM. ------------------------------------------------------------------------------------------------------------------------------------ 3.5 NGC1399 FOS/BL ACQ/ 1.0 MIRROR TYPE=UP 1 70S 4 1 ONBOARD ACQ FOR 4 PEAK SCAN-STEP=0.7 SEARCH-SIZE=4 Comments: FOS/BL ACQ/PEAK ADDED BY STSCI DUE TO NEW OPERATING RULES FOR SINGLE-SIDE ACQS. POINTING WILL BE SPLIT FROM RED SIDE POINTING BY SAA PASSAGE, SO THE POINTING FOR THE FOS/BL OBS CANNOT BE GUARANTEED TO BE SAME AS FOR FOS/RD. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC1399 FOS/BL ACCUM 1.0 G130H 1 10453.2 8 5 1 Comments: S/N IS MEAN PER ANGSTROM. ESPECIALLY PREFER DARK TIME FOR THIS OBSERVATION. THIS IS NOT A REQUIREMENT BUT A PREFERENCE. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3647c [ 8] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC3610 FOS/RD ACQ/ 1.0 MIRROR TYPE=UP 1 30S 20 4 1 ONBOARD ACQ FOR 6- PEAK SCAN-STEP=0.7 7 SEARCH-SIZE=4 SEQ 5-8 WITHIN 36 H Comments: WANT TO MAXIMIZE S/N, SO DO A COARSE PEAKUP TO GET WITHIN ABOUT 0.35" OF BRIGHTEST SPOT. ALTHOUGH NUCLEUS PER SE IS NOT THE TARGET, WE WISH ALL OBS FOR BOTH SIDES TO BE TAKEN WITH SAME POINTING. STSCI SAYS NOT POSSIBLE. ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC3610 FOS/RD ACCUM 1.0 G190H 1 5835.6S 10 6 1 Comments: S/N IS MEAN PER ANGSTROM. ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC3610 FOS/RD ACCUM 1.0 G270H 1 3531.6S 20 7 1 Comments: S/N IS MEAN PER ANGSTROM. ------------------------------------------------------------------------------------------------------------------------------------ 7.5 NGC3610 FOS/BL ACQ/ 1.0 MIRROR TYPE=UP 1 60S 4 1 ONBOARD ACQ FOR 8 PEAK SCAN-STEP=0.7 SEARCH-SIZE=4 Comments: FOS/BL ACQ/PEAK ADDED BY STSCI DUE TO NEW OPERATING RULES FOR SINGLE-SIDE ACQS. POINTING WILL BE SPLIT FROM RED SIDE POINTING BY SAA PASSAGE, SO THE POINTING FOR THE FOS/BL OBS CANNOT BE GUARANTEED TO BE SAME AS FOR FOS/RD. ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC3610 FOS/BL ACCUM 1.0 G130H 1 10453.2 4 5 1 Comments: S/N IS MEAN PER ANGSTROM. FLUX IS VERY UNCERTAIN ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 3647c [ 9] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters TYPE SCAN-STEP=0.7 SEARCH-SIZE=4 TYPE=UP ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 15.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category NEARBY GALAXIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-3; SEQ 1-4 WITHIN 36 H; CYCLE 2 / 1-8; ONBOARD ACQ FOR 4; ONBOARD ACQ FOR 6-7; SEQ 5-8 WITHIN 36 H; ONBOARD ACQ FOR 8; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G190H G270H G130H ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1399 ESO358-45 PGC13418 NGC3610 UGC6319 PGC34566 ------------------------------------------------------------------------------------------------------------------------------------