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Register a new userMapping Excitation in the Inner Regions of the Planetary Nebula NGC 5189 using HST WFC3 Imaging
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Added by
Ashkbiz Danehkar PhD
Publication date
2017
fields
Physics
and research's language is
English
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The planetary nebula (PN) NGC 5189 around a Wolf-Rayet [WO] central star demonstrates one of the most remarkable complex morphologies among PNe with many multi-scale structures, showing evidence of multiple outbursts from an AGB progenitor. In this study we use multi-wavelength Hubble Space Telescope Wide Field Camera 3 (WFC3) observations to study the morphology of the inner 0.3 pc $times$ 0.2 pc region surrounding the central binary that appears to be a relic of a more recent outburst of the progenitor AGB star. We applied diagnostic diagrams based on emission line ratios of H$alpha$ $lambda$6563, [O III] $lambda$5007, and [S II] $lambdalambda$6717,6731 images to identify the location and morphology of low-ionization structures within the inner nebula. We distinguished two inner, low-ionization envelopes from the ionized gas, within a radius of 55 arcsec ($sim$ 0.15 pc) extending from the central star: a large envelope expanding toward the northeast, and its smaller counterpart envelope in the opposite direction toward the southwest of the nebula. These low-ionization envelopes are surrounded by a highly-ionized gaseous environment. We believe that these low-ionization expanding envelopes are a result of a powerful outburst from the post-AGB star that created shocked wind regions as they propagate through the previously expelled material along a symmetric axis. Our diagnostic mapping using high-angular resolution line emission imaging can provide a novel approach to detection of low-ionization regions in other PNe, especially those showing a complex multi-scale morphology.
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We present the results of a comprehensive, near-UV-to-near-IR Hubble Space Telescope WFC3 imaging study of the young planetary nebula (PN) NGC 6302, the archetype of the class of extreme bi-lobed, pinched-waist PNe that are rich in dust and molecular gas. The new WFC3 emission-line image suite clearly defines the dusty toroidal equatorial structure that bisects NGC 6302s polar lobes, and the fine structures (clumps, knots, and filaments) within the lobes. The most striking aspect of the new WFC3 image suite is the bright, S-shaped 1.64 micron [Fe II] emission that traces the southern interior of the east lobe rim and the northern interior of the west lobe rim, in point-symmetric fashion. We interpret this [Fe II] emitting region as a zone of shocks caused by ongoing, fast (~100 km/s), collimated, off-axis winds from NGC 6302s central star(s). The [Fe II] emission and a zone of dusty, N- and S-rich clumps near the nebular symmetry axis form wedge-shaped structures on opposite sides of the core, with boundaries marked by sharp azimuthal ionization gradients. Comparison of our new images with earlier HST/WFC3 imaging reveals that the object previously identified as NGC 6302s central star is a foreground field star. Shell-like inner lobe features may instead pinpoint the obscured central stars actual position within the nebulas dusty central torus. The juxtaposition of structures revealed in this HST/WFC3 imaging study of NGC 6302 presents a daunting challenge for models of the origin and evolution of bipolar PNe.
We present the first direct image of the high-metallicity gas component in a planetary nebula (NGC 6778), taken with the OSIRIS Blue Tunable Filter centered on the O II 4649+50 angstroms optical recombination lines (ORLs) at the 10.4m Gran Telescopio Canarias. We show that the emission of these faint O II ORLs is concentrated in the central parts of the planetary nebula and is not spatially coincident either with emission coming from the bright [O III] 5007 angstroms collisionally excited line (CEL) or the bright H alpha recombination line. From monochromatic emission line maps taken with VIMOS at the 8.2m Very Large Telescope, we find that the spatial distribution of the emission from the auroral [O III] 4363 line resembles that of the O II ORLs but differs from nebular [O III] 5007 CEL distribution, implying a temperature gradient inside the planetary nebula. The centrally peaked distribution of the O II emission and the differences with the [O III] and H I emission profiles are consistent with the presence of an H-poor gas whose origin may be linked to the binarity of the central star. However, determination of the spatial distribution of the ORLs and CELs in other PNe, and a comparison of their dynamics is needed to further constrain the geometry and ejection mechanism of the metal-rich (H-poor) component and hence, understand the origin of the abundance discrepancy problem in PNe.
The globular cluster (GC) system of our Galaxy contains four planetary nebulae (PNe): K 648 (or Ps 1) in M15, IRAS 18333-2357 in M22, JaFu 1 in Pal 6, and JaFu 2 in NGC 6441. Because single-star evolution at the low stellar mass of present-epoch GCs was considered incapable of producing visible PNe, their origin presented a puzzle. We imaged the PN JaFu 1 with the Hubble Space Telescope (HST) to obtain photometry of its central star (CS) and high-resolution morphological information. We imaged IRAS 18333-2357 with better depth and resolution, and we analyzed its archival HST spectra to constrain its CS temperature and luminosity. All PNe in Galactic GCs now have high-quality HST data, allowing us to improve CS mass estimates. We find reasonably consistent masses between 0.53 and 0.58 Msun for all four objects, though estimates vary when adopting different stellar evolutionary calculations. The CS mass of IRAS 18333-2357, though, depends strongly on its temperature, which remains elusive due to reddening uncertainties. For all four objects, we consider their CS and nebular masses, their morphologies, and other incongruities to assess the likelihood that these objects formed from binary stars. Although generally limited by uncertainties (~0.02 Msun) in post-AGB tracks and core mass vs. luminosity relations, the high-mass CS in K 648 indicates a binary origin. The CS of JaFu 1 exhibits compact bright [O III] and Halpha emission, like EGB 6, suggesting a binary companion or disk. Evidence is weaker for a binary origin of JaFu 2.
We have mapped the extended narrow line region (ENLR) of NGC 3393 on scales of $rlesssim4^{primeprime}$ ($sim1,$kpc) from the nucleus using emission line images of H$alpha,lambda6563$, [O III]$lambda5007$, and [S II]$lambdalambda6717,6731$ taken with HST as part of the CHandra survey of Extended Emission line Regions in nearby Seyfert galaxies (CHEERS). By mapping these lines onto a spatially resolved Baldwin-Phillips-Terlevich (BPT) diagram, we investigate the impact of feedback from a Compton-thick AGN on its circumnuclear ISM. We find the expected Seyfert-like emission within the ionization bicone ($lesssim3^{primeprime}$; 770 pc). We also find a new, figure 8 shaped LINER cocoon enveloping the bicone and defining a sharp ($lesssim100;$pc) transition between higher and lower ionization zones. These data illustrate the morphological dependence of ionization states of the ENLR relative to bicone and host gas geometries.
Planetary nebulae expand on time scales of 10^3-10^4 yr. For nearby objects, their expansion can be detected within years to decades. The pattern of expansion probes the internal velocity field and provides clues to the nebula ejection mechanism. In the case of non-symmetric nebulae, and bipolar nebulae in particular, it can also provide information on the development of the morphology. We have measured the expansion proper motions in NGC 6302 from two epochs of HST imaging, separated by 9.43 years. This is used to determine the expansion age and the structure of the velocity field. We use HST images in the [N II] 6583{AA} filter from HST WF/PC2 and WFC3. The proper motions were obtained for a set of 200 individual tiles within 90 of the central star. The velocity field shows a characteristic linear increase of velocity with radial distance (a so-called Hubble flow). It agrees well with a previous determination by Meaburn et al. (2008), made in a lobe further from the star, which was based on a much longer time span. The pattern of proper motion vectors is mostly radial and the origin is close to the position of the central star directly detected by Szyszka et al. (2009). The results show that the lobes of NGC 6302 were ejected during a brief event 2250 pm 35yr ago. In the inner regions there is evidence for a subsequent acceleration of the gas by an additional 9.2 km/s, possibly related to the onset of ionization. The dense and massive molecular torus was ejected over 5000yr, ending about 2900yr ago. The lobes were ejected after a short interlude (the jet lag) of sim 600 yr during a brief event. The torus and lobes orig- inate from separate mass-loss events with different physical processes. The delay between the cessation of equatorial mass loss and the ejection of the lobes provides an important constraint for explaining the final mass-loss stages of the progenitor stellar system.
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