Sub-Arcsecond Morphology of Planetary Nebulae (original) (raw)
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Morphological Structures of Planetary Nebulae
Publications of the Astronomical Society of Australia, 2010
Since various structural components of planetary nebulae manifest themselves differently, a combination of optical, infrared, submm, and radio techniques is needed to derive a complete picture of planetary nebulae. The effects of projection can also make the derivation of the true 3-D structure difficult. Using a number of examples, we show that bipolar and multipolar nebulae are much more common than usually inferred from morphological classifications of apparent structures of planetary nebulae.
On the Origin of Morphological Structures of Planetary Nebulae
Galaxies
We suggest that most of the mass in planetary nebulae (PNe) resides in the equatorial region and the spherical envelope and the optically bright lobes of PNe are in fact low-density cavities cleared out by fast outflows and photoionized by UV photons leaked from the torus. The nature of multi-polar PNe is discussed under this framework.
The Astronomical Journal, 1998
First results from a Hubble Space T elescope Wide Field Planetary Camera 2 Ha imaging survey of young planetary nebulae (PNs) are reported. The PNs have been selected on the basis of their low excitation characteristics. All objects imaged so far show highly aspherical morphology, with a majority characterized by multipolar bubbles distributed roughly point-symmetrically around the central star. In some objects, bipolar ansae or collimated radial structures are seen, indicating the presence of jets, whereas in others bright structures near the minor axes indicate the presence of disks or torii. The complexity, organization, and symmetry of the above structures lead us to propose that the primary agent for shaping PNs is high-speed collimated outÑows or jets that operate during the late asymptotic galactic branch (AGB) and/or early post-AGB evolutionary phase, and not a preexisting equatorial density enhancement as envisioned in the currently popular model. These outÑows carve out a complex imprint within an intrinsically spherical AGB circumstellar envelope (CSE). Subsequent expansion of a hot, tenuous stellar wind from the post-AGB star inside the imprinted AGB CSE then produces the observed PN, whose shape and structure depend in detail on how the characteristics of the jets change with time.
Astron J, 2011
Using Hubble Space Telescope images of 119 young planetary nebulae, most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-planetary nebulae, which are the immediate progenitors of planetary nebulae (PNs). Unlike previous classification studies, we have focussed primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many cases, physical causes are readily suggested by the geometry, along with the kinematics that have been measured in some systems. Secondary characteristics in our system such as ansae indicate the impact of a jet upon a slower-moving, prior wind; a waist is the signature of a strong equatorial concentration of matter, whether it be outflowing or in a bound Keplerian disk, and point symmetry indicates a secular trend, presumably precession, in the orientation of the central driver of a rapid, collimated outflow.
Sub-arcsecond optical imaging of Proto-Planetary Nebulae
Symposium - International Astronomical Union, 1997
Subarcsecond V and I images have been obtained of 13 new protoÈplanetary nebulae (PPNs). (0A .75) We Ðnd nine of them to be resolved, with sizes up to 3A, and two others to perhaps also be extended. Of the nine, four appear to be elliptical in shape. Thus an aspherical morphology is demonstrated to commonly exist early in the transition between the asymptotic giant branch and planetary nebula phases. The results of this larger observational study, together with the previously published imaging studies, indicate that most PPNs are elliptical (or bipolar) in shape.
High‐Resolution Imaging of Two Bipolar Proto–Planetary Nebulae
The Astrophysical Journal, 1996
Sub-arcsecond resolution V and I images have been obtained for two protoÈplanetary nebulae. Both are found to show a deÐnite bipolar morphology. A circumstellar disk is clearly seen in the V [I color image, suggesting that the bipolar lobes are due to starlight scattered into the polar openings. This indicates that bipolar morphologies develop early in the evolution of planetary nebulae, even before the onset of photoionization. Subject headings : circumstellar matter È planetary nebulae : general È stars : AGB and post-AGB
Atlas of monochromatic images of planetary nebulae
We present an atlas of more than one hundred original images of planetary nebulae (PNe). These images were taken in a narrow-band filter centred on the nebular emission of using two moderate-aperture telescopes the [N ii] during several observing campaigns at the Complejo Astronómico El Leoncito (CASLEO) and the Estación Astrofísica de Bosque Alegre (EABA), both in Argentina. The data provided by this atlas represent one of the most extensive image surveys of PNe in [N ii]. We compare the new images with those available in the literature and briefly describe all cases in which our [N ii] images reveal new and interesting structures.
Planetary Nebulae: Observational Properties, Mimics and Diagnostics
Publications of the Astronomical Society of Australia, 2010
The total number of true, likely and possible planetary nebulae (PN) now known in the Milky Way is nearly 3000, double the number known a decade ago. The new discoveries are a legacy of the recent availability of wide field, narrowband imaging surveys, primarily in the light of H-alpha. In this paper, we summarise the various PN discovery techniques, and give an overview of the many types of objects which mimic PN and which appear as contaminants in both Galactic and extragalactic samples. Much improved discrimination of classical PN from their mimics is now possible based on the wide variety of high-quality multiwavelength data sets that are now available. We offer improved taxonomic and observational definitions for the PN phenomenon based on evaluation of these better diagnostic capabilities. However, we note that evidence is increasing that the PN phenomenon is heterogeneous, and PN are likely to be formed from multiple evolutionary scenarios. In particular, the relationships between some collimated symbiotic outflows and bipolar PN remain uncertain.
Asymmetrical Planetary Nebulae II: From Origins to Microstructures
2000
Narrow-band images of the core of the extraordinary polypolar planetary nebula KjPn 8 have been obtained with the WFPC2 camera on board the Hubble Space Telescope. Spasmodic bipolar ejections, in changing directions have occurred over thousands of years to create KjPn 8. The central star is finally revealed in these observations and its compact nebular core is resolved into a remarkably young ≈ 500 years old, elliptical ionized ring. The highest speed bipolar outflows are perpendicular to this central ring which is identified as the latest event in the creation of this nebula. The formation history of KjPn 8 has involved two distinct planetary nebula-like events, probably originating from a binary core evolution with components of similar mass.
Spectroscopy and imaging of newly discovered planetary nebulae
Astronomy and Astrophysics Supplement Series, 1996
The major purpose of this paper was to prove or disprove the nature of planetary nebula (PN) candidates in the northern hemisphere, taken from an internal list. We present spectroscopic observations and imaging of fifteen PNe, twelve of them identified for the first time. Another two candidates turned out to be an emission-line galaxy and an H ii region. All observed PNe represent evolved stages, their angular diameter ranging from 8 to 90 , and exhibit very low surface brightnesses. The three largest and faintest nebulae each host a central star of magnitude 18 to 20 m .