![ÈHST PC images of the GO sample taken through the F502N Ðlter. L eft : Raw calibrated images ; right : RL restored images. The orientation of the raw images is the same as that indicated for the restored images. Each frame is 80 ] 80 pixels, or All images are displayed on a logarithmic 3A .5 ] 3A .5. scale from the peak to a factor of 100 below.](https://www.researchgate.net/profile/Michael-Dopita/publication/231031801/figure/fig1/AS:650479138795531@1532097720852/EHST-PC-images-of-the-GO-sample-taken-through-the-F502N-Dlter-L-eft-Raw-calibrated_Q320.jpg)
![ÈAs but for the GTO PC and FOC images. The FOC frames shown are 166 ] 166 pixels, or Fig. 1, 3A .7 ] 3A .7.](https://www.researchgate.net/profile/Michael-Dopita/publication/231031801/figure/fig3/AS:650479138795533@1532097720931/EAs-but-for-the-GTO-PC-and-FOC-images-The-FOC-frames-shown-are-166-166-pixels-or-Fig_Q320.jpg){kind=tracking}
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Hubble Space Telescope Observations of Planetary Nebulae in the Magellanic Clouds. VII. Cycle 3 and Archive Narrowband [O III] 500.7 nanometer Imaging
Abstract and Figures
We present the continuation of our analysis of narrowband [O III] images, obtained using the Hubble Space Telescope (HST), of planetary nebulae (PNs) in the Magellanic Clouds. Six objects, five in the Large Magellanic Cloud, are observed as part of the General Observer program. An additional 15 objects are retrieved from the HST archive. The majority of the images are obtained prior to the first maintanence and refurbishment mission and are dominated by nebular [O III] 500.7 nm emission: the PN central stars are generally not seen. The raw images are deconvolved using 100 iterations of the Richardson-Lucy image restoration algorithm. The nebular dimensions and morphologies are determined. The nebular dynamical ages are derived using [O III] 500.7 nm expansion velocities from the literature. Using the techniques presented in Paper IV, the measured nebular ages are compared to theoretical evolutionary ages for H-burning and He-burning PN nuclei. Approximately 50% of the PN central stars are He burners in both the Large and Small Magellanic Clouds.
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The LMC is ideal for studying the coevolution of planetary nebulae (PNs) and their central stars in that the debilitating uncertainties of the Galactic PN distance scale and selection biases from attenuation by interstellar dust do not apply. We present images and analyze slitless spectra that were obtained in a survey of Large Magellanic Cloud PNs. These data on 29 targets were obtained with the Hubble Space Telescope (HST) using the Space Telescope Imaging Spectrograph. The data permit us to determine the nebular dimensions and morphology in the monochromatic light of several emission lines, including those that have traditionally been used for morphological studies in the Galaxy: Hα, [N II] λ6583, and [O III] λ5007, plus others of varying ionization including [O I], He I, and [S II]. Together with the 31 resolved LMC PNs for which monochromatic images exist in the HST archive, these data show that the incidence of nonsymmetric nebulae, including bipolar nebulae (which is an indicator of Population I ancestry in the Galaxy), is significantly higher than that reported for the Galaxy. The onset of asymmetric features appears even in very young nebulae (with dynamical ages of ~1400 yr), suggesting that at least the gross features of the nebular morphology may be more closely tied to PN formation and that subsequent shaping of the expanding envelope by the radiation field and wind from the central star may play the lesser role of amplifying these gross features. There is some evidence of evolution between two morphological types in the sense that bipolar core nebulae may evolve to pure bipolars late in the PN lifetime.
During an X-ray survey of the Small Magellanic Cloud, carried out with the XMM-Newton satellite, we detected significant soft X-ray emission from the central star of the high-excitation planetary nebula SMP SMC 22. Its very soft spectrum is well fit with a non local thermodynamical equilibrium model atmosphere composed of H, He, C, N, and O, with abundances equal to those inferred from studies of its nebular lines. The derived effective temperature of 1.5x10^5 K is in good agreement with that found from the optical/UV data. The unabsorbed flux in the 0.1-0.5 keV range is about 3x10^{-11} erg cm^-2 s^-1, corresponding to a luminosity of 1.2x10^37 erg/s at the distance of 60 kpc. We also searched for X-ray emission from a large number of SMC planetary nebulae, confirming the previous detection of SMP SMC 25 with a luminosity of (0.2-6)x10^35 erg/s (0.1-1 keV). For the remaining objects that were not detected, we derived flux upper limits corresponding to luminosity values from several tens to hundreds times smaller than that of SMP SMC 22. The exceptionally high X-ray luminosity of SMP SMC 22 is probably due to the high mass of its central star, quickly evolving toward the white dwarf's cooling branch, and to a small intrinsic absorption in the nebula itself. Comment: Accepted for publication on Astronomy and Astrophysics
[abridged] We present 52-93 micron spectra obtained with Spitzer in the MIPS-SED mode, of a representative sample of luminous compact far-IR sources in the LMC. These include carbon stars, OH/IR AGB stars, post-AGB objects and PNe, RCrB-type star HV2671, OH/IR red supergiants WOHG064 and IRAS05280-6910, B[e] stars IRAS04530-6916, R66 and R126, Wolf-Rayet star Brey3a, Luminous Blue Variable R71, supernova remnant N49, a large number of young stellar objects, compact HII regions and molecular cores, and a background galaxy (z~0.175). We use the spectra to constrain the presence and temperature of cold dust and the excitation conditions and shocks within the neutral and ionized gas, in the circumstellar environments and interfaces with the surrounding ISM. Evolved stars, including LBV R71, lack cold dust except in some cases where we argue that this is swept-up ISM. This leads to an estimate of the duration of the prolific dust-producing phase ("superwind") of several thousand years for both RSGs and massive AGB stars, with a similar fractional mass loss experienced despite the different masses. We tentatively detect line emission from neutral oxygen in the extreme RSG WOHG064, with implications for the wind driving. In N49, the shock between the supernova ejecta and ISM is revealed by its strong [OI] 63-micron emission and possibly water vapour; we estimate that 0.2 Msun of ISM dust was swept up. Some of the compact HII regions display pronounced [OIII] 88-micron emission. The efficiency of photo-electric heating in the interfaces of ionized gas and molecular clouds is estimated at 0.1-0.3%. We confirm earlier indications of a low nitrogen content in the LMC. Evidence for solid state emission features is found in both young and evolved object; some of the YSOs are found to contain crystalline water ice. Comment: Accepted for publication in The Astronomical Journal. This paper accompanies the Summer 2009 SAGE-Spec release of 48 MIPS-SED spectra, but uses improved spectrum extraction. (Fig. 2 reduced resolution because of arXiv limit.)
Self-consistent photoionization modeling of 44 Magellanic Cloud PNe is used to construct an H-R diagram for the central stars in both Clouds and is used to obtain the nebular chemical abundances and the physical parameters of the nebulae. The type I PNe are the youngest PNe in the clouds, have the highest core masses, and lie on the descending branch of the evolutionary tracks. These objects show correlated He and N/O abundance enhancements. The nebulae mass of the optically thick objects is well correlated with the nebular radius. Clear evidence is found for an abundance scatter in the material which formed the precursor star of the PNe in both Clouds. The metallicity range in the LMC is a factor of about 10, while that in the SMC is about 3-4. A core-mass:metallicity relationship is discovered for the LMC and is interpreted as a transformed age:metallicity relationship.
Optical spectroscopy in the range 3300-7800 A is presented for a total of 37 planetary nebulae in the LMC and seven in the SMC. Reddening estimates from Balmer line ratios have been determined, and the line intensities have been dereddened accordingly. Nebular forbidden O III electron temperatures, and where measurable forbidden S II densities, are derived. Forbidden O II electron densities are recalculated using appropriate electron temperatures. Zanstra temperatures are derived for 22 objects possessing detectable stellar continua. These temperatures are in agreement with photoionization modeling of this sample. 35 refs.
Using the Faint Object Camera on-board the Hubble Space Telescope, we have obtained images of four planetary nebulae (PNe) in the Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the LMC. Each nebula was imaged through two narrow-band filters isolating [O III] λ5007 and Hβ, for a nominal exposure time of 1000 s in each filter. Significant detail is evident on the raw images and, after deconvolution using the Richardson-Lucy algorithm, structures as small as 0″.06 are easily discernible. In [O III], SMC N5 shows a circular ring structure, with a peak-to-peak diameter of 0″.26 and a FWHM of 0″.35, while SMC N2 shows an elliptical ring structure with a peak-to-peak diameter of 0″.26 × 0″.21 (FWHM 0″.40 × 0″.35). The expansion ages corresponding to the observed structures in SMC N2 and N5 are of the order of 3000 yr. Such low ages appear more easy to reconcile with helium-burning rather than hydrogen-burning central star evolutionary tracks. LMC N201 is very compact, with a FWHM of 0″.21 in Hβ. The Type I PN LMC N66 is a multipolar nebula, with the brightest part having an extent of about 2″ and with fainter structures extending over 4″. The [O III] image reveals structures unprecedented for a planetary nebula, with several bright knots and faint loops visible outside the two main bright lobes.
The spherical aberration in the primary mirror of the Hubble Space Telescope causes more than 80% of the light from a point source to be spread into a halo of radius of 2–3 arcsec. The point spread function (PSF) is both time variant (resulting from spacecraft jitter and desorption of the secondary mirror support structure) and space variant (owing to the Cassegrain repeater optics in the Wide Field / Planetary Camera). A variety of image restoration algorithms have been utilized on HST data with some success, although optimal restorations require better modeling of the PSF and the development of efficient restoration algorithms that accommodate a spacevariant PSF. The first HST servicing mission (December 1993) will deploy a corrective optics system for the Faint Object Camera and the two spectrographs and a second generation WF/PC with internal corrective optics. As simulations demonstrate, however, the restoration algorithms developed now for aberrated images will be very useful for removing the remaining diffraction features and optimizing dynamic range in post-servicing mission data.
The aim of this study is to derive the masses of the central stars (CSPN) for a large sample of the planetary nebulae (PN). These masses, M ∗ , are derived from the observed PN positions in three diagnostic diagrams and their comparison with evolutionary tracks of model PN. Two of the diagrams, namely L Zan ( H ) versus T Zan ( H ) and M v versus R neb , have already been used in numerous studies. The third one, S H β versus S V , has recently been introduced by Górny, Stasińska & Tylenda (1996, hereinafter GST96). Here S H β is the nebular surface brightness in H β and S v is defined as F v /(πθ 2 ), where F v is the stellar flux in the V band and θ is the observed nebular angular radius.
As an introduction to the symposium the related problems of the distances, structures and chemical compositions of the Magellanic Clouds are reviewed.
The planetary camera onboard HST is used to image six planetary nebulae in the Magellanic Clouds: LMC-SMP7, 37, 61, 67, 101, and SMC-SMP22\@. The narrow-band F502N filter isolates the strong nebular [O III] emission line at 500.7 nm. The images are obtained from August to October 1993, prior to the first HST servicing mission. Each image is restored with 100 iterations of the standard Richardson-Lucy method, which gives a reliable representation of the nebular morphology. For the major and minor axes of each object, a Gaussian function is convolved with the HST PSF and compared with the unrestored nebular profile. For 5 of the 6 objects, the results are consistent to within 30% of the outer nebular radii determined from photoionisation modelling of ground-based optical spectrophotometry. The exception, LMC-SMP101, is optically thin and has a radius of ~ 0.3 pc; ~ 5 times the radius determined from the photoionisation model. The time elapsed since the onset of the AGB superwind is calculated by dividing the nebular radius by the published [O III] expansion velocity for each object. The values range from 585 years for LMC-SMP37 to 5620 years for LMC-SMP101. Central star ages inferred using published stellar parameters from photoionisation models and published theoretical stellar evolutionary tracks, are at least a factor of two greater than the dynamical ages. For LMC-SMP7, t_evol/t_dyn = 14000/585 ~ 20. The HST [O III] fluxes, measured with a 3.3('') -radius circular aperture, are consistent with ground-based [O III] aperture photometry to within 0.15 mag. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for this work was provided by NASA through grant number GO-2266 from the STScI\@.