Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4040c Report Date: 09-May-96:19:06 Version: ********** Check-in Date: ********** 1.Proposal Title: POST ASYMPTOTIC GIANT BRANCH EVOLUTION IN THE MAGELLANIC CLOUDS. CONT OF 2266 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS GO 2266 Sub Category LATE EVOLUTION ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Michael A. Dopita MT. STROMLO AND SIDING SPRIN AUSTRALIA (011 61) 62-49 SENIOR FELLOW ------------------------------------------------------------------------------------ 7. Abstract Planetary Nebulae (PN) represent a critical stage of stellar evolution which is still poorly understood. We still lack reliable observational estimates of stellar luminosity, mass, effective temperature and age, which could be used to constrain evolutionary models, and determine key data such as mass-loss rates, He shell flash phases and the role of dredge-up. This proposal represents the first stage in a systematic and definitive study using HST observations, which will require approximately a further 150 hours for completion, of a large sample of nebulae at known distance in the Magellanic Clouds. The following observations allow us to derive all parameters needed for proper confrontation between theory and observation: * Direct PC imaging to detect central stars and to derive the physical dimensions, masses, ages, and spatial structure of the nebulae. * FOS spectrophotometry of the central stars and nebulae in the range 1150 - 2332 Angstroms. This data will be used in combination with stellar models to derive the effective temperature, bolometric luminosity, and mass of each of the exciting stars. The combination of these parameters with the dynamical age of the PN will define the evolutionary tracks in the Luminosity/T-eff diagram. We will use two independent ionisation codes to interpret the FOS spectra, optical and IR spectra, and the ionisation structure derived from the PC images. This analysis will yield chemical abundances of many elements, including the astrophysically important species He, C, N, O, and Si. ------------------------------------------------------------------------------------ 8. Scientific Key Words: STARS:HB STAR, INTERSTELLAR MEDIUM:PLANETARY NEBULA, GALAXY:MAGELLANIC CLOUDS, ASTROPHYSICS:EVOLUTION, STELLAR POPULATION, ABUNDANCE ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 40.00 par: 0 10. Num targs pri: 19 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4040c PI: Dr. Michael A. Dopita Proposal Title: POST ASYMPTOTIC GIANT BRANCH EVOLUTION IN THE MAGELLANIC CLOUDS. CONT OF 2266 ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Dr Peter R Wood MOUNT STROMLO AND SIDING SPRING AUSTRALIA OBSERVATORIES Dr Stephen J Meatheringham MOUNT STROMLO AND SIDING SPRING AUSTRALIA OBSERVATORIES Dr Ralph C Bohlin SPACE TELESCOPE SCIENCE USA INSTITUTE Dr Holland C Ford SPACE TELESCOPE SCIENCE USA INSTITUTE Dr Patrick J Harrington UNIVERSITY OF MARYLAND USA Dr Theodore P Stecher GODDARD SPACE FLIGHT CENTER USA Dr Stephen P Maran GODDARD SPACE FLIGHT CENTER USA Dr Louise B Webster(Deceased) UNIVERSITY OF NEW SOUTH WALES AUSTRALIA Dr Michael A. Dopita MOUNT STROMLO AND SIDING SPRING AUSTRALIA OBSERVATORIES ------------------------------------------------------------------------------------ 3. Description of proposed observations. Imaging Program: The Magellanic Cloud PN range in size from 0.05 - 4.0 arcseconds, with a typical size of about 0.6 arcseconds (Jacoby 1980; Wood, Bessell and Dopita 1986; Wood et. al. 1987). Consequently, they are ideally suited for imaging with the PC camera. We prefer to use the PC rather than the FOC, because the FOC has a limited dynamic range, would saturate on many of our objects, and does not carry the required set of filters. Our [O III] 5007 Angstrom (F502N) images are designed to give a typical signal to noise of 20 per pixel to provide data on angular diameters and nebular morphology (spherical, bipolar, multiple shell, etc.), which in conjunction with our ground-based [O III] expansion velocity measurements will provide a dynamical age model. UV Spectrophotometry: We are proposing FOS spectrophotometry in the range 1150 - 2332 Angstroms using the G130H and G190H gratings. We aim to achieve an average signal to noise in the nebular continuum of 5 per pixel. Since the Magellanic Clouds are close enough that even the faintest PN can be detected, the flux and spectral distribution of the PN nuclei can be measured over their entire ~5 mag in luminosity. Our aim is to accomplish this objective, and to achieve a good detection of the central star against the nebular continuum, even when the stellar flux is only 10% of this nebular continuum. This objective will also ensure that uniform, high quality, high dynamic range nebular spectra are obtained for the full range of nebular conditions. These data will be combined with our ground-based data of comparable quality covering the wavelength range 3200 - 10000 Angstroms. In the decade of frequency covered by these observations, we will see emission lines of the astrophysically important elements such as He, C, N, O, Si and S in the full range of ionisation stages expected to be present in the nebula. For this reason, and also because the allowable nebular models are strongly constrained by the imaging results, we expect that the chemical abundances we will derive will be much more accurate than any previously obtained. References: Jacoby, G., 1980, Ap. J. Suppl. Ser., vol. 42, p. 1 Wood, P.R., Bessell, M.S., and Dopita, M.A., 1986, Ap. J., vol. 311, p. 632 Wood, P.R., Meatheringham, S.J., Dopita, M.A., and Morgan, D.H., Ap. J., vol. 320, p. 178 NOTE: ALL OBSERVATIONS NOW DONE ON ONE SIDE ( BLUE ) PER PI's OK. 03/27/92 - RAL NOTE: METHOD OF ACQUISITION REVISED. PN ACQUIRED DIRECTLY USING BINARY SEARCH. 08/04/92. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The angular diameters of the Magellanic Cloud PN line in the range 0.05 - 4.0 arcseconds, ideally suited to the HST capabilities. the dimensions or morphologies of these objects cannot, in general, be obtained from the ground. Preliminary ground-based work has been done, as far as it is possible, using direct imaging and image reconstruction (Jacoby 1980; Wood et. al. 1987) or speckle interferometry (Wood, Bessell, and Dopita 1986). However, imaging resolves only the largest, and speckle interferometry resolves only the brightest nebulae, leaving the vast majority of objects unresolved. Some of us have obtained low resolution UV spectra of a few of these objects using the IUE satellite. However, only the brightest objects are observable, many of the same objects chosen for the GTO program. The UV data is crucial for measurement of the stellar flux distribution and to obtain densities and ionic abundances for dominant ionisation stages of many elements. Only the combination of high resolution and a spectral range which extends shortward of the peak in the hydrogen two-photon nebular continuum (about 1450 Angstroms) will enable us to detect the star in the cases where the nebular continuum is strong. Our HST program is supported by a comprehensive and continuing ground-based program. We have used the 1-metre, 2.3-metre and 3.9-metre telescopes at Siding Spring to measure fluxes, sizes, expansion velocities, radial velocities and nebular spectra from 3200 to 10000 Angstroms. These observations already provide an excellent set of homogeneous and high-quality data which gives the best possible ground-based characteristics of the Magellanic Cloud population of PN. this data set will allow us to extend our population classifications from the HST subset to the entire population of PN in the Magellanic Clouds. References: Jacoby, G., 1980, Ap. J. Suppl. Ser., vol. 42, p. 1 Wood, P.R., Bessell, M.S., and Dopita, M.A., 1986, Ap. J., vol. 311, p. 632 Wood, P.R., Meatheringham, S.J., Dopita, M.A., and Morgan, D.H., Ap. J., vol. 320, p. 178 Page 4 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. Our observational objective is no less than to make the definitive study of PN evolution in the Magellanic Clouds. This program represents the first stage in this quest. To complete this objective will require approximately a further 150 hours of HST time. Our sample is therefore carefully chosen to eliminate selection bias in excitation class and flux, down to log(Flux(H-Beta)) ~13.7. By contrast, the GTO program shows a strong bias towards bright, high excitation, optically thick nebulae. This bias ensures that only PN with more massive nuclei are observed, and nothing can be concluded about the mass or age distribution from the GTO sample. By having a sufficiently large number of objects in the HR diagram we aim to study both the mass distribution and the rate of evolution through the HR diagram. The latter constraint is a particularly important one for stellar evolution; it will tell us at what phase of evolution on the AGB, and when in a Helium shell flash cycle PN ejection occurs. Abundances derived from these observations will show which PN nuclei have C-star progenitors, which, combined with the mass estimates will give mass, and hence age, limits for C-star formation, which can be linked with existing studies of this class of star. With the GTO program objects included, the total sample of some 25 PN will provide a suitable sample to begin to group the planetaries into statistically significant families in the three prime observational quantities. Our imaging program has been configured to provide [O III] images with an average S/N of 15 per pixel (850 photoelectrons per pixel) to ensure that high- quality images are obtained in the same line in which the expansion velocity profile is measured. The counts/pixel N are given in terms of the surface flux density (F_surf) by : log(N) = - f(Phi) C + log(F_surf), where C has the values 12.34, 12.28 for the F502N and F487N, filters, respectively. f(Phi) is a function of the diameter, and is calculated from the HST PSFfrom models. The spectroscopy program is configured to give a measurement of the C III] 1960/1990 Angstrom density and to give the nebular flux distribution to an accuracy of 3% in bins of 50 Angstroms. This ensures that the flux and flux distribution of the central star can be measured in the 1 arcsecond aperture down to 10% of the nebular continuum contributions. A mean extinction E(B-V) of 0.15 and an LMC or SMC- like extinction law has been assumed. The counts/diode/second C-d, is given in terms of the flux at 1650 Angstroms (F_1650)by : log(C_d) =- f(Phi) C + log(F_1650), where C has the values 13.53 (G130H, blue digicon) and 13.69 (G190H, red digicon). The red digicon rapidly increases in sensitivity at longer wavelengths so exposure times are shorter. The function f(Phi) is a function of the diameter of the PN, accounting for spherical abberation and is calculated from a modelling of the PSF and the PN. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. As high-quality astrometric determination of the nebular centroid will be obtained on the basis of the PC images, we are requesting that the direct imaging observations precede the spectrophotometric observations by 2-4 months in order that these images can be evaluated and used for accurate astrometry. For the spectrophotometric observations, we expect to acquire the PN by a binary search of the FOS on a nearby bright star followed by a blind offset to the PN. NOTE: METHOD OF ACQUISITION REVISED. PN ACQUIRED DIRECTLY USING BINARY SEARCH. 08/04/92. Page 5 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. All PC images and FOS spectra will be reduced at STScI and then distributed by H.Ford and R.Bohlin to the team members. The dynamical ages of the nebulae will be derived by creating models of expanding prolate shells with varying azimuthal intensities whose projections onto the sky reproduce the [O III] line profiles (already obtained for the whole sample, Dopita et. al. 1985, 1988) and the PC image structure. The software needed for this program has already been written by H.Ford and his collaborators. We plan to combine the FOS UV spectrophotometry with ground-based and near-IR spectrophotometry to produce dereddened spectra. Theoretical models of the nebular continuum and of the central star will be used to separate the two continuum contributions and to place the star on the L-T(eff) diagram. By using the dynamical age already obtained, we will compare the evolutionary tracks implied for the PN nuclei with the theoretical evolutionary models (e.g. Wood and Faulkner 1986). This will enable us to determine the mass distribution of the PN nuclei, to determine whether PN ejection occurs at the time of the Helium shell flash, and to put strong observational restraints on the post-AGB mass-loss. Using the observed parameters of the central star, the FOS spectrophotometry and ionisation structure implied by the PC images, we will construct detailed photoionisation models using independent codes by Harrington, and by Dopita and Binette. The nebular size and structure, the shape of the stellar spectrum, and the ratio of stellar to nebular continua will enable us to obtain the mean ionisation parameter (Q), the ionisation temperature (T*), and the optical thickness of the nebula, which together define the nebular model. The FOS spectra are vital in the determination of the abundances of the dominant ionic species of N, C and Si. Likewise the ratio of the C III] doublet at 1906, 1909 Angstroms will give the electron density in the region of the PN containing the dominant ionisation stage. From the complete spectrophotometric data we will be able to derive the abundances of the elements : He, C, N, O, Ne, S, Cl, and Ar, and possibly, Mg, Fe and Ni as well. We wish to stress that the PC nebular images and the wealth of FOS ultraviolet data will enable us to construct models with a level of detail which has previously been obtained in only a few Galactic PN such as NGC7662 (Harrington et. al. 1982), and IC3918 (Clegg et. al. 1987). References: Clegg, R.E.S., Harrington, J.P., Barlow, M.J., and Walsh, J.R., 1987, Ap. J., vol. 314, p. 575 Dopita, M.A., Ford, H.C., Lawrence, C.J., and Webster, B.L., 1985, Ap. J., vol. 296, p. 390 Dopita, M.A., Meatheringham, S.J., Webster, B.L., and Ford, H.C.,1988, Ap. J., vol. 327, p. 639 Harrington, J.P., Seaton, M.J., Adams, S., and Lutz, J.H., 1982, M.N.R.A.S., vol. 199, p. 517 Wood, P.R., and Faulkner, D.J., 1986, Ap. J., vol. 307, p. 659 ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Since the full analysis of the data will take a total of three years, we request that release of the data be delayed a full year after the completion of the observational program. Full archival use will be made of data obtained under the GTO program on Magellanic Cloud PN as this is released. Primary team responsibilities are as follows: 1. Image reduction, astrometry, analysis and distribution : Ford and 2. FOS data reduction and distribution : Bohlin and Meatheringham 3. Analysis and evolution of central stars : Dopita, Wood, Bohlin, Maran and Stecher 4. Nebular modelling and chemical composition : Dopita, Harrington, and Maran 5. Analysis of stellar populations and astrophysical interpretation : all team. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). The manpower, fiscal and hardware resources necessary to support the work of the P.I. and the other Australian members of this group will be supplied from within the internal budget of MSSSO as necessary. Funding will also be available to support any short overseas visits that may be necessary to coordinate activities of the various team members, as summarised in question 8. Page 6 ------------------------------------------------------------------------------------ 11. Address Information Name: MICHAEL A. DOPITA Category: PI Institution: MT. STROMLO AND SIDING SPRING OBS Address: PRIVATE BAG WODEN P.O. City: CANBERRA, ACT State: Zip Code: 2606 Country: AUSTRALIA Telephone: (011 61) 62 49-0212 Telex (or e-mail): AA62270 CANOPUS ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4040c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 118 LMC-SMP85 H,502 RA = 05H 40M 30.87S +/- 2000.0 V = 232 1 F-CONT(1650) = 3.6 +/- 1.8 E-15 N69 0.02S, 2 F-LINE(5007) = 1.3 +/- 0.1 E-12 DEC = -66D 17' 37.53" +/- 3 SURF-LINE(5007) = 2.6 +/- 0.8 E-11 0.1", 4 SURF-LINE(4861) = 7.7 +/- 2.5 E-12 PLATE-ID=06B0 5 SURF-CONT(5470) = 5.4 +/- 2.7 E-14 6 W-LINE(5007) = 1.0, SIZE = 0.25 Comments: PN POSITION DETERMINED FROM GASP: PLATES=06B0,02I7. (PLATE 06B0 USED FOR COORDS HERE.) ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4040c [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 DEFINE # FOS/BL ACQ/ 4.3 MIRROR BRIGHT=720000 1 1S 1 1 BINACQ BINARY FAINT=660 Comments: ACQUIRE PN DIRECTLY. ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE # FOS/BL ACCUM 1.0 G130H 1300 1 1S # 1 1 FOS130 Comments: 1989 SENSITIVITY FIGURES IN THE EXPOSURE AND S/N CALCULATIONS. ------------------------------------------------------------------------------------------------------------------------------------ 3 DEFINE # FOS/BL ACCUM 1.0 G190H 1900 1 1S # 1 1 FOS190 Comments: 1989 SENSITIVITY FIGURES IN THE EXPOSURE AND S/N CALCULATIONS. ------------------------------------------------------------------------------------------------------------------------------------ 4 DEFINE # FOS/BL ACCUM 1.0 PRISM 5007 1 1S # 3 1 CALPR Comments: 1989 SENSITIVITY FIGURES IN THE EXPOSURE AND S/N CALCULATIONS ? ------------------------------------------------------------------------------------------------------------------------------------ 5 DEFINE # FOS/BL ACCUM 1.0 G270H 2700 1 1S # 3 1 FOS270 Comments: 1989 SENSITIVITY FIGURES IN THE EXPOSURE AND S/N CALCULATIONS. ------------------------------------------------------------------------------------------------------------------------------------ 6 USE LMC-SMP85 X17 SEQ 6-11 NO GAP BINACQ ONBOARD ACQ FOR 7- 11 CYCLE 1 Comments: EXPOSURE TIME DERIVED FROM OPTICAL SPECTRUM AND FOS EXPOSURE SIMULATOR. ------------------------------------------------------------------------------------------------------------------------------------ 7 LMC-SMP85 FOS/BL ACQ 4.3 MIRROR 1 63S 3 1 CYCLE 1 Comments: PICTURE REQUIRED TO RECORD FINAL POINTING POSITION. ------------------------------------------------------------------------------------------------------------------------------------ 8 USE LMC-SMP85 X270 50 CYCLE 1 CALPR ------------------------------------------------------------------------------------------------------------------------------------ 9 USE LMC-SMP85 X270 5 CYCLE 1 FOS190 ------------------------------------------------------------------------------------------------------------------------------------ 10 USE LMC-SMP85 X180 5 CYCLE 1 FOS270 ------------------------------------------------------------------------------------------------------------------------------------ 11 USE LMC-SMP85 X600 5 CYCLE 1 FOS130 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4040c [ 9] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACCUM ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT FAINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 40.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category LATE EVOLUTION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SEQ 6-11 NO GAP; ONBOARD ACQ FOR 7-11; CYCLE 1; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G130H G190H PRISM G270H ------------------------------------------------------------------------------------------------------------------------------------ Target Names LMC-SMP85 N69 ------------------------------------------------------------------------------------------------------------------------------------