7513( 11) - 04/05/99 16:12 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7513 Version: 11 Check-in Date: 05-Apr-1999 16:12:05 1.Proposal Title: The Stellar Content Of Giant HII Regions ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Claus Leitherer Space Telescope Science Institute CoI: Rosa Gonzalez-Delgado Space Telescope Science Institute N CoI: Timothy M. Heckman Johns Hopkins University N CoI: Gra\.zyna Stasinska Observatoire de Meudon N ------------------------------------------------------------------------------------ 5. Abstract We propose to obtain STIS spectroscopy of 2 giant HII regions over the wavelength range 1200 Angstrom\ -- 10000 Angstrom. All objects show Wolf-Rayet features in the optical, suggesting ages of 3 -- 6 Myr. Therefore the starburst age, which is often diffi cult to disentangle from other parameters, is known a priori. The metallicity range is between 1/10 solar and slightly below solar. The observations will provide an important consistency test for the latest generation of starburst models. The nebular emi ssion-line spectrum will be modeled with a photoionization code using stellar spectra from evolutionary synthesis models. The stellar continuum and absorption-line spectrum in the ultraviolet offers a second, independent method to constrain the hot stell ar population. Strong, blueshifted stellar-wind lines of C IV\ and [S II]v\ will be visible in this spectral range. We will derive the properties of the massive-star population both from the nebular spectrum and from the ste llar-wind lines. The use of HS T al lows us to observe the entire spectral range through the same slit. Comparison of the results will shed light on the maturity of these new evolutionary synthesis techniques. ------------------------------------------------------------------------------------ 7513( 11) - 04/05/99 16:12 - [ 2] Observations Description ------------------------ The objects will be observed with STIS and aperture 52X0.1 for the CCD and 52x0.5 for the FUV-MAMA. The choice of the aperture is dictated by S/N and spectral resolution requirements in the ultraviolet. We wish to perform line- profile fits to the strong [ S II]v\\ and C IV\\ lines, which have Doppler broadenings of 1000 -- 2000 kms. A spectral resolution of at least half this value (500 kms) is required. The HII regions fill the aperture in the dispersion direction so that the corresponding resolution is 4 pixels (Table 13.18), or 2.4 Angstrom, which is sufficient to reach our goal of 500 kms. The S/N requirement is S/N = 25 per resolution element. Different ages and IMF's of the starburst population lead to variations of the Si IV and C IV profiles, as d iscussed by Leitherer et al. (1995). In order to constrain the age to within +/-1 Myr and the IMF exponent to +/- 0.5, S/N = 25 is necessary. Although we carefully selected the most compact HII regions from the existing FOC imagery, all of them exceed the sl it width of 0.1''. Typical diameters are around 0.3''. We simulated the amount of light encompassed by the 52X0.1 slit from measurements of the brightness profiles on the FOC images. Note that C.L. is co -I on the original HST program which obtained th e FOC images and is therefore familiar with the data. All objects range between 5 * 10^-16 to 3 * 10^-15 erg s^-1 cm^-2 AA^-1 at 2200 Angstrom, with a median value of 1 * 10^-15 erg s^-1 cm^-2 AA^-1. We adopted the median value for the count-rate calculat ions of all five HII regions at 1450 Angstrom\\ as well, considering most starburst regions being essentially flat or rising with lambda^-2 towards shorter wavelengths. The theoretically expected (and for some galaxies actually observed) continuum level i n the optical is a few times 10^-16 erg s^-1 cm^-2 AA^-1. However, the S/N of the continuum in the optical is not an important consideration, since we are primarily interested in the emission lines. Integration times in the opti cal using the CCD are insi gnifican t (see below). We performed extensive simulations using various grating/slit combinations in order to determine the optimum configuration. In principle, G140M would have been a good compromise between efficiency and spectral resolution but the wa velength range per tilt of this grating is only 55 Angstrom, so that multiple settings would have been required. The result of our simulations is that G140L and 52X0.1, 0.5 are best suited to reach our scientific goals. A signal-to-noise of 25 per resolut ion element is reached in 8000 sec for a flux level of 1 * 10^-15 erg s^-1 cm^-2 AA^-1. For the optical we use gratings G430L and G750M with the 52X0.1 aperture and the CCD detector. The scientific goal is to measure line fluxes of the usual strategic lin es and determine the slope of the stellar continuum. We find that exposure times of 5 and 10 minutes are required for gratings G750M and G430L, respectively. The S/N in the spatial direction will be high enough to allow us to investig ate variations of th e nebular prop erties along the slit. Our strategy then is as follows. Part of the first orbit is required for the guide star acquisition (9 min) and the target acquisition. We will use a diffuse acquisition (10 min), followed by a peak-up into the 0.1'' slit (5 min). The remaining time in the first orbit is sufficient to obtain the two CCD exposures with grating G430L and G750M, including set-up time and read-out. Four more orbits are required to do the MAMA-FUV spectroscopy. Assuming four guide-star rea quisitions (24 min), 8 min set-up time, and three additional wavecals and overheads (12 min and 3 min), leaves about 150 minutes of data taking, which meets the science requirement. This sequence will be followed for all 2 targets, leading to a total requ est for 10 orbits. Real Time Justification ----------------------- No requirements. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7513( 11) - 04/05/99 16:12 - [ 3] Data Distribution Paper Products: Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7513( 11) - 04/05/99 16:12 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3049 GALAXY, STARBURST RA=9H 54M 49.4S +/- 0.1S, DEC=9D J2000 V = 15.2 16' 15.9" +/- 1" F(5500)=3+/-1e-15 F(1500)=1+/-1e-14 2 TOL89 GALAXY, STARBURST RA=14H 1M 19.9S +/- 0.1S, DEC=- J2000 V = 15.2 33D 4' 9.9" +/- 1" F(5500)=3+/-1e-15 F(1500)=1+/-1e-14 3 TOLOLO89 GALAXY, STARBURST RA=14H 1M 19.92S +/- 0.1S, DEC=- J2000 V = 15.2 33D 4' 10.7" +/- 1" F(5500)=3+/-1e-15 F(1500)=1+/-1e-14 Comments: Slightly revised position based on early acq 7513( 11) - 04/05/99 16:12 - [ 5] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Early Acq for 10 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3049 STIS/F ACCUM F25SRF2 MIRROR 1 15 M MAX DUR 100% UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3049 STIS/C ACCUM F28X50L MIRROR CR-SPLIT=4 1 4 M SAME POS AS 1 MAX DUR CD P 100% ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3049 STIS/C ACCUM F28X50O MIRROR CR-SPLIT=2 1 15 M SAME POS AS 1 CD III ------------------------------------------------------------------------------------------------------------------------------------ 7513( 11) - 04/05/99 16:12 - [ 6] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Early Acq for 20 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 TOL89 STIS/F ACCUM F25SRF2 MIRROR 1 15 M MAX DUR 100% UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 TOL89 STIS/C ACCUM F28X50L MIRROR CR-SPLIT=4 1 4 M SAME POS AS 1 MAX DUR CD P 100% ------------------------------------------------------------------------------------------------------------------------------------ 3 TOL89 STIS/C ACCUM F28X50O MIRROR CR-SPLIT=2 1 15 M SAME POS AS 1 CD III ------------------------------------------------------------------------------------------------------------------------------------ 7513( 11) - 04/05/99 16:12 - [ 7] Visit: 10 Visit Priority: Visit Requirements: AFTER 01 BY 60 D TO 120 D ORIENT 267D TO 267D On Hold Comments: Additional Comments: Orientation +180 deg also ok Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3049 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1 S ONBOARD ACQ FOR 2 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3049 STIS/C ACQ/PEA 52X0.1 MIRROR 1 5 S ONBOARD ACQ FOR 3-8 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3049 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=2 1 13.5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3049 STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=2 1 13.5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC3049 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC3049 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC3049 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC3049 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7513( 11) - 04/05/99 16:12 - [ 8] Visit: 20 Visit Priority: Visit Requirements: ORIENT 314D TO 316D On Hold Comments: Additional Comments: Orientation +180 deg also ok Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 TOLOLO89 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 5 S ONBOARD ACQ FOR 2 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 TOLOLO89 STIS/C ACQ/PEA 52X0.1 MIRROR 1 20 S ONBOARD ACQ FOR 3-8 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 TOLOLO89 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=2 1 13.5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 4 TOLOLO89 STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=2 1 13.5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 5 TOLOLO89 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 TOLOLO89 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 TOLOLO89 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8 TOLOLO89 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7513( 11) - 04/05/99 16:12 - [ 9] Summary Form for Proposal 7513 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25SRF2 F28X50LP F28X50OIII 52X0.1 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/FUV-MAMA STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ACQ ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=4 CR-SPLIT=2 ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements MAX DUR 100% SAME POS AS 1 MAX DUR 100% SAME POS AS 1 AFTER 01 BY 60 D TO 120 D ORIENT 267D TO 267D ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3-8 ORIENT 314D TO 316D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G750M G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC3049 TOL89 TOLOLO89 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 6581 1425 ------------------------------------------------------------------------------------------------------------------------------------