We present the kinematics of a sample of bipolar planetary nebulae (PNe) which cover a wide range of observed morphologies and collimation degrees, from bipolar PNe with a marked equatorial ring and wide lobes to highly collimated objects. We use an empirical model in order to derive the expansion velocity, collimation degree, and inclination angle of the PN with respect to the plane of the sky. The equatorial expansion velocities measured in the objects in our sample are always in the low to medium range (3-16km/s),while their polar expansion velocities range from low to very high (18-100 km/s). None of the objects in our sample, even those that show an extreme collimation degree, seem to be (kinematically) younger than ~1000 yr. We compare our results with the state-of-the-art theoretical models for the formation of bipolar PNe. We find good agreement between the observed expansion velocities and numerical models that use magnetic fields with stellar rotation as collimation mechanism.
We report our search for optically thick radio cores in sixteen narrow-waist bipolar nebulae. Optically thick cores are a characteristic signature of collimated ionized winds. Eleven northern nebulae were observed with the Very Large Array (VLA) at 1.3 cm and 0.7 cm, and five southern nebulae were observed with the Australia Telescope Compact Array (ATCA) at 6 cm and 3.6 cm. Two northern objects, 19W32 and M 1-91, and three southern objects, He 2-25, He 2-84 and Mz 3, were found to exhibit a compact radio core with a rising spectrum consistent with an ionized jet. Such jets have been seen in M…
We discuss the interaction of the slow wind blown by an asymptotic giant branch (AGB) star with a collimated fast wind (CFW) blown by its main sequence or white dwarf companion, at orbital separations in the range of several AU to about 200 AU. The CFW results from accretion of the AGB wind into an accretion disk around the companion. The fast wind is collimated by the accretion disk. We argue that such systems are the progenitors of bipolar planetary nebulae and bipolar symbiotic nebulae with a very narrow equatorial waist between the two polar lobes. We conduct a population synthesis study o…
I discuss some observational properties of aspherical nebulae around massive stars, and conclusions inferred for how they may have formed. Whether or not these ideas are applicable to the shaping of planetary nebulae is uncertain, but the observed similarities between some PNe and bipolar nebulae around massive stars is compelling. In the well-observed case of Eta Carinae, several lines of observational evidence point to a scenario where the shape of its bipolar nebula resulted from an intrinsically bipolar explosive ejection event rather than an interacting winds scenario occurring after ejec…
We present near-IR narrow-band continuum-subtracted images in the H$_2$ $2.122μ$m, and Br$γ$ $2.166μ$m emission lines for a sample of 15 bipolar planetary nebulae. H$_2$ emission was definitely detected for most of the objects in this sample (13 out of 15). The very high H$_2$ detection rate supports the idea that bipolar planetary nebulae have important reservoirs of molecular material and offer suitable physical conditions for the excitation of H$_2$. The strength of the H$_2$ emission and the H$_2$/Br$γ$ flux ratio are found to correlate with the morphology of the bipolar nebulae observed. …
In this work we investigate how a circumstellar disk affects the radiation emitted by an embedded star. We show correlations obtained from broad-band observations of bipolar nebulae indicating that an orientation effect is at play in these systems. The FIR radiation relative to total radiation increases with inclination while the NIR and BVR fractions decrease. This is an expected effect if we consider the system as being made up of a dense dusty disk being irradiated by a hot star. We calculate 2-D models to try and reproduce the observed behavior with different disk and star configurations.
We present results of our search for collimated ionized winds in bipolar nebulae using the Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA). Our search is motivated by the discovery of an ionized jet in the bipolar nebula M 2-9 (Lim & Kwok 2003) that may be responsible for sculpting the nebula's mirror-symmetric structure. To determine if such jets are a common feature of bipolar nebulae, we searched for optically-thick radio cores - a characteristic signature of ionized jets - in 11 northern nebulae with the VLA at 1.3 cm and 0.7 cm, and in 5 southern nebulae with the A…
Using a radiation-hydrodynamics code I follow the formation of planetary nebulae around stars of different mass. Because a more massive central star evolves much faster than a lower mass one, it is to be expected that this will affect the formation of the PN. For the stars I use the evolutionary tracks for remnants with masses of 0.605 M0 and 0.836 M0, taken from Bloecker (1995). The AGB wind is assumed to be concentrated in a thin disk, which in models without evolving stars leads to the formation of a bipolar nebula. I find that in the case of the 0.836 M0 remnant the nebula indeed acquires …
We present thermal-IR images of three extreme bipolar objects, M2-9, Mz3, and He2-104. They are bipolar planetary nebulae with bright central stars and are thought to be powered by symbiotic binary systems. The mid-IR images spatially resolve the SEDs of the central engines from the surrounding nebulae. A warm dust component of several hundred degrees can account for the core emission, while a cooler component of about 100 K produces the more extended emission from the bipolar lobes. In every case, the dust mass for the unresolved core region is orders of magnitude less than that in the extend…
We present milliarsecond-resolution maps of the SiO maser emission $v$=1 J=2--1 (3 mm) in the bipolar post-AGB nebula OH 231.8+4.2, and compare them with our previous observations of the $v$=2 J=1--0 line (7 mm). Our observations show that the SiO masers arise in several bright spots forming a structure elongated in a direction perpendicular to the symmetry axis of the nebula. This, and the complex velocity gradient observed, is consistent with the presence of an equatorial torus in rotation and with an infall of material towards the star.
We show that there are strong links between certain types of asymmetrical Planetary Nebulae (PNe) and symbiotic stars. Symbiotics are binaries and several have extended optical nebulae all of which are asymmetrical and ~-40% are bipolar. Bipolar PNe are likely to be formed by binaries and share many properties with symbiotic nebulae (SyNe). Some PNe show point symmetry which is naturally explained by precession in a binary system. M2-9 has both point and plane symmetry, and has been shown to have a binary central object. We show that inclination on the sky affects the observed properties of bi…
We present low and high resolution long-slit spectra of three bipolar planetary nebulae (PNe) with bright central cores: A79, He2-428 and M1-91. He2-428 and M1-91 have high density (from 10^3.3 to 10^6.5 cm^-3) unresolved nebular cores that indicate that strong mass loss/exchange phenomena are occurring close to their central stars. An F0 star is found at the centre of symmetry of A79; its reddening and distance are consistent with the association of the star with the nebula. The spectrum of the core of He2-428 shows indications of the presence of a hot star with red excess emission, probably …
We show that the inclination to the line of sight of bipolar nebulae strongly affects some of their observed properties. We model these objects as having a spherically symmetric Planetary Nebula and a dusty equatorial density enhancement that produces extinction that varies with the viewing angle. Our sample of 29 nebulae taken from the literature shows a clear correlation between the inclination angle and the near-IR and optical photometric properties as well as the apparent luminosity of the objects. As the inclination angle increases --the viewing angle is closer to the equatorial plane-- t…
This work presents three dimensional, magneto-hydrodynamical simulations of the formation and early evolution of a subgroup of planetary nebulae that exhibit a variety of point-symmetric structures. For bipolar nebulae, the formation of point-symmetric nebular shapes along the inner borders of their opposing lobes and/or collimated outflows or jets internal or external to their cavities, is reproduced by considering a steady misalignment of the magnetic collimation axis with respect to the symmetry axis of the bipolar wind outflow, defined perpendicular to the equatorial density enhancement. E…
We present ESO NTT high resolution echelle spectroscopy of the central stars (CSs) of eight southern bipolar planetary nebulae (PNe) selected for their asymmetry. Our aim was to determine or place limits on the magnetic fields of the CSs of these nebulae, and hence to explore the role played by magnetic fields in nebular morphology and PN shaping. If magnetic fields do play a role, we expect these CSs to have fields in the range $10^2 - 10^7$ G from magnetic flux conservation on the reasonable assumption that they must evolve into the high field magnetic white dwarfs. We were able to place an …
We have obtained X-ray observations of the bipolar planetary nebulae (PNe) NGC 2346 and NGC 7026 with XMM-Newton. These observations detected diffuse X-ray emission from NGC 7026 but not from NGC 2346. The X-ray emission from NGC 7026 appears to be confined within the bipolar lobes of the PN and has spectral properties suggesting a thermal plasma emitting at a temperature of 1.1 +0.5/-0.2 times 10^6 K. The X-ray spectrum of NGC 7026 is modeled using nebular and stellar abundances to assess whether a significant amount of nebular material has been mixed into the shocked-wind, but the results of…
Expansion velocities (Vexp) of different ions and line widths at the base of the lines are measured and analyzed for 24 PNe with [WC]-type nuclei (WRPNe), 9 PNe ionized by WELS (WLPNe) and 14 ordinary PNe. A comparative study of the kinematical behavior of the sample clearly demonstrates that WRPNe have in average 40-45% larger Vexp, and possibly more turbulence than WLPNe and ordinary PNe. WLPNe have velocity fields very much alike the ones of ordinary PNe, rather than the ones of WRPNe. All the samples (WRPNe, WLPNe and ordinary PNe) show expansion velocities increasing with age indicators, …
High-resolution near-infrared images and moderate resolution spectra were obtained of the bipolar nebulae M~2--9 and AFGL 2688. The ability to spatially and spectrally resolve the various components of the nebulae has proved to be important in determining their physical structure and characteristics. In M~2--9, the lobes are found to have a double-shell structure. Analysis of \h2\ line ratios indicates that the \h2\ emission is radiatively excited. A well-resolved photodissociation region is observed in the lobes. The spectrum of the central source is dominated by H recombination lines and a s…
We report the discovery of two new circumstellar ring nebulae in the western Carina Nebula. The brighter object, SBW1, resembles a lidless staring eye and encircles a B1.5 Iab supergiant. Its size is identical to the inner ring around SN1987A, but SBW1's low N abundance indicates that the star didn't pass through a RSG phase. The fainter object, SBW2, is a more distorted ring, is N-rich, and has a central star that seems to be invisible. We discuss these two new nebulae in context with rings around SN1987A, Sher25, HD168625, RY Scuti, WeBo1, SuWt2, and others. The ring bearers fall into two gr…
Multi-object and multi-fiber spectrographs on 4 and 8 meter telescopes make it possible to use extragalactic planetary nebulae (PNe) in the outer halos of early-type galaxies as kinematical tracers, where classical techniques based on integrated stellar light fail. Until now, published PNe radial velocity samples are small, with only a few tens of radial velocity measurements (except for a few cases like NGC 5128 or M31), causing uncertainties in the mass and angular momentum estimates based on these data. To quantify these uncertainties, we have made equilibrium models for spherical galaxies,…
We have carried out a spatial-kinematical study of three proto-planetary nebulae, IRAS 16594-4656, Hen 3-401, and Rob 22. High-resolution H2 images were obtained with NICMOS on the HST and high-resolution spectra were obtained with the Phoenix spectrograph on Gemini-South. IRAS 16594-4656 shows a "peanut-shaped" bipolar structure with H2 emission from the walls and from two pairs of more distant, point-symmetric faint blobs. The velocity structure shows the polar axis to be in the plane of the sky, contrary to the impression given by the more complex visual image and the visibility of the cent…
We report results from a program of high-resolution spectral mapping of rotational H_2 emission from bipolar planetary and pre-planetary nebulae. Long-slit spectra obtained with the NOAO Phoenix near-infrared spectrometer allow us to probe the molecular kinematics of these nebulae at moderate spatial resolution. We find strong evidence of a component of rotation in the equatorial H_2 emission from the Egg nebula (RAFGL 2688). In this nebula and in the pre-planetary nebula RAFGL 618, the H_2 kinematics point to the recent emergence of high-velocity polar flows, which likely mark the fairly sudd…
We investigate the development of bipolar outflows during the early post-AGB evolution. A sample of ten OH/IR stars is observed at high angular resolution, including bipolar nebulae (OH231.8+4.2), bright post-AGB stars (HD 101584) and reflection nebulae (e.g. Roberts 22). The IRAS colour--colour diagram separates the sample into different types of objects. One group may contain the progenitors to the (few) extreme bipolar planetary nebulae. Two objects show colours and chemistry very similar to the planetary nebulae with late IR-[WC] stars. One object is a confirmed close binary. A model is pr…
The structure of the dusty circumstellar envelopes (CSEs) of proto-planetary nebulae (PPNs) reveals the mass-loss history of these sources and how such histories may differ for elliptical (SOLE) and bipolar (DUPLEX) PPNs. To study the PPN structures via dust-scattered linearly polarized starlight, we have compiled the imaging-polarimetric data for all 18 evolved stars that have been obtained to date with NICMOS on-board the Hubble Space Telescope (HST). This alternative imaging technique provides a unique way to probe the distribution of dust grains that scatter light around evolved stars. The…
Magnetic fields are an important but largely unknown ingredient of planetary nebulae. They have been detected in oxygen-rich AGB and post-AGB stars, and may play a role in the shaping of their nebulae. Here we present SCUBA sub-millimeter polarimetric observations of four bipolar planetary nebulae and post-AGB stars, including two oxygen-rich and two carbon-rich nebulae, to determine the geometry of the magnetic field by dust alignment. Three of the four sources (NGC 7027, NGC 6537 and NGC 6302) present a well-defined toroidal magnetic field oriented along their equatorial torus or disk. NGC 6…
We present a statistical analysis of a complete sample (255) of northern planetary nebulae (PNe). Our analysis is based on morphology as a main parameter. The major morphological classes are: round (26 % of the sample), elliptical (61 %), and bipolar (13 %) PNe. About a half of the round and 30 % of the elliptical PNe present multiple shells. Round PNe have higher galactic latitude (| b| = 12) and galactic height (<z> = 753 pc), than the elliptical (|b| = 7,<z> = 308 pc) and bipolar (|b| = 3, <z>=179 pc). This possibly implies a different progenitor mass range across morphology, as a different…
A recent spectroscopic analysis of central stars of planetary nebulae (CSPNe) claims that the sample includes five CSPNe with masses very close to the Chandrasekhar limit of white dwarfs. This claim should be verified or discarded from the available kinematical and chemical abundance information. Kinematical parameters are extracted from Galactic orbits and compared with parameters expected for populations of different ages. The chemistry of the nebulae is compared with average values for different types. The reported high masses are not supported by our investigation. The claimed high central…
Hypersonic bipolar outflows are a ubiquitous phenomena associated with both young and highly evolved stars. Observations of Planetary Nebulae, the nebulae surrounding Luminous Blue Variables such as $η$ Carinae, Wolf Rayet bubbles, the circumstellar environment of SN 1987A and Young Stellar Objects all revealed high velocity outflows with a wide range of shapes. In this paper I review the current state of our theoretical understanding of these outflows. Beginning with Planetary Nebulae considerable progress has been made in understanding bipolar outflows as the result of stellar winds interact…
The LMC is ideal for studying the co-evolution of planetary nebulae (PNe) 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 slit-less spectra which were obtained in a survey of Large Magellanic Cloud PNe. These data on 29 targets were obtained with 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 hav…
We acquired spectra of 24 LMC PNe in the 1150--3000 Årange in order to determine carbon and other ionic abundances. The sample more than doubles the number of LMC PNe with good quality UV spectra in this wavelength range, and whose optical images are available in the {\it HST} archive. The {\it Space Telescope Imaging Spectrograph} was used with a very large aperture to obtain virtually slit-less spectra, thus the monochromatic images in the major nebulae emission lines are also available. The analysis of the data shows extremely good quality spectra. This paper presents the emission lines ide…
Symbiotic Miras give a nice practical demonstration of the formation of bipolar and highly aspherical nebulae as a consequence of interaction in detached binaries. We believe that these binary systems are among the most promising candidates for the progenitors of bipolar planetary nebulae. We present a list of the optically extended nebulae known to date around symbiotic Miras, and illustrate their properties using recent HST and ESO-NTT [NII] images of He 2-104 and He 2-147.
Two bipolar proto-planetary nebulae, IRAS16594-4656 and IRAS17150-3224, have been detected in various molecular lines, namely CO, ^{13}CO, HCN and CN, and remain undetected in several other species. CO(J=2-1) and CO(J=3-2) line profiles are compared to new spectra of similar PPN candidates, previously undetected in CO(J=2-1): CPD-53^{o}5736, IRAS17106-3046, IRAS17245-3951 and IRAS17441-2411. CO(J=2-1) maps of IRAS16594-4656 and IRAS17150-3224 show that both PPNe have little separation between blue, centre and red-shifted emission, and also that the CO(J=2-1) emission is of a similar size to th…
Asymptotic Giant Branch (AGB) stars generally have spherically symmetric envelopes, whereas most post-AGB stars and Planetary Nebulae (PNe) show axisymmetric circumstellar envelopes. While various mechanisms for axisymmetric circumstellar structures may explain the shapes of PNe, they do not address how the shape of the circumstellar shell evolves. Here we address the temporal changes in the axisymmetry of AGB star envelopes, and in particular the development of the torus required in the Generalized Interacting Stellar Winds (GISW) model. Assuming (1) an AGB star rotates with sufficient angula…
High-resolution near-infrared HST NICMOS (F160W, F222M) images and polarization (2 um) observations were made of four bipolar proto-planetary nebulae (PPNs): IRAS 17150-3224, IRAS 17441-2411, IRAS 17245-3951, and IRAS 16594-4656. The first three of these are viewed nearly edge-on, and for the first time the central stars in them are seen. Color maps reveal a reddened torus between the bipolar lobes in the edge-on cases, with bluer lobes. The polarization values are high, with maximum values ranging from 40 to 80%. The polarization patterns are basically centrosymmetric, with some deviations in…
We present high spectral resolution maps of near-infrared molecular hydrogen emission from the bipolar pre-planetary nebulae RAFGL 2688 and RAFGL 618, obtained with the NOAO Phoenix spectrometer. The measured velocity gradients along the polar axes of both nebulae indicate that the highest velocity gas lies closest to the central stars. These results support the suggestion that the polar H_2 emission regions of both nebulae contain shocked gas formed as fast (~50-150 km/s), collimated, post-asymptotic giant branch (AGB) winds collide with slower-moving (~10-20 km/s) material previously ejected…
We report NICMOS wide-band and polarimetric observations of four proto-planetary nebulae. Molecular hydrogen emission is detected near the ends of the bipolar lobes of IRAS 17150-3224, which is evidence for the interaction of a fast, collimated outflow with the remnant of the asymptotic giant branch wind.
We report the detection of several new circumstellar disks seen in silhouette in the outskirts of the Orion nebula and M43, detected as part of our Halpha survey of Orion with the HST/ACS. Several of the disks show bipolar reflection nebulae, microjets, or temporal variability. Two disks in our sample are large and particularly noteworthy: A nearly edge-on disk, d216-0939, is located several arcminutes northwest of M43 and resembles the famous HH30 disk/jet system in Taurus. It drives the 0.15 pc long bipolar outflow HH667, and exhibits a remarkable asymmetric reflection nebula. With a diamete…
The young planetary nebulae play an important role in stellar evolution when intermediate- to low-mass stars (0.8 $\sim$ 8 M$_\odot$) evolve from the proto-planetary nebulae phase to the planetary nebulae phase. Many young planetary nebulae display distinct bipolar structures as they evolve away from the proto-planetary nebulae phase. One possible cause of their bipolarity could be due to a binary origin of its energy source. Here we report our detailed investigation of the young planetary nebula, Hubble 12, which is well-known for its extended hourglass-like envelope. We present evidence with…
We present the results of far-infrared imaging of extended regions around three bipolar pre-planetary nebulae, AFGL 2688, OH 231.8+4.2, and IRAS 16342$-$3814, at 70 and 160 $μ$m with the MIPS instrument on the Spitzer Space Telescope. After a careful subtraction of the point spread function of the central star from these images, we place constraints on the existence of extended shells and thus on the mass outflow rates as a function of radial distance from these stars. We find no apparent extended emission in AFGL 2688 and OH 231.8+4.2 beyond 100 arcseconds from the central source. In the case…
We present our recent results on mm-wave CO observations of proto-planetary nebulae. These include high-resolution interferometric maps of various CO lines in three well known bipolar PPNe: M1-92, M2-56 and OH231.8+4.2. The global properties of the high velocity molecular emission in post-AGB sources have been also studied, by means of high-sensitivity single dish observations of the J=1-0 and 2-1 lines of 12CO and 13CO. We discuss the implications of these results to constrain the origin of the post-AGB molecular high-velocity winds and the shaping of bipolar PPNe and PNe. In addition, we als…
Planetary nebulae are thought to be formed when a slow wind from the progenitor giant star is overtaken by a subsequent fast wind generated as the star enters its white dwarf stage$^{1}$. A shock forms near the boundary between the winds, which creates a relatively dense shell that provides the characteristic appearance of a planetary nebula. A spherically symmetric wind will produce a spherically symmetric shell, yet over half of known planetary nebulae are not spherical; rather, they are elliptical or bipolar in shape$^{2}$. While a magnetic field could launch and collimate a bipolar outflow…
Observations suggest that many, if not all, post AGB systems evolve through an aspherical outflow phase. Such outflows require a sufficient engine rotational energy which binaries can provide. Via common envelope evolution, binaries can directly eject equatorial outflows or produce poloidal outflows from magnetized accretion disks around the primary or secondary. We discuss how accretion driven magnetohydrodynamic outflow models all make similar predictions for the outflow power and speed and we distinguish between the launch vs. propagation regimes of such outflows. We suggest that the high v…
We present images and slitless spectra which were obtained in HST surveys of Planetary Nebulae (PNe) in both the Large and Small Magellanic Clouds, using the Space Telescope Imaging Spectrograph. These new data on 59 PNe (54 in the LMC and five in the SMC) permit us to determine the nebular dimensions and morphology in the monochromatic light of several emission lines: Halpha, [N II] lambda 6583 and [O III] lambda 5007, plus others of varying ionization, including [O I], He I, and [S II]. We describe the nebular morphology and related features in detail. This survey, when combined with similar…
This review describes some general properites of proto-planetary nebulae with particular emphasis on the recent work of morpholgical studies. The weight of observational evidence shows that proto-planetary nebulae (PPNe) are most certainly axisymmetric like planetary nebulae. Recent work suggests two subclasses of PPNe optical morphology, DUst-Prominent Longitudinally-EXtended (DUPLEX) and Star-Obvious Low-level Elongated (SOLE). Radiative transfer models of an example DUPLEX PPN and SOLE PPN, presented here, support the interpretation that DUPLEX and SOLE are two physically distinct types of …
Nebulae around symbiotic Miras look very much like genuine planetary nebulae, although they are formed in a slightly different way. We present near infrared photometry of known and suspected symbiotic nebulae obtained with the Deep Near Infrared Southern Sky Survey (DENIS). We demonstrate that the near infrared colours are an excellent tool to distinguish symbiotic from genuine planetary nebulae. In particular we find that the bipolar planetary nebulae M 2-9 and Mz 3 are in fact symbiotic Miras. Further observations on prototype symbiotic Miras prove that the proposed classification scheme wor…
We conduct 2D axisymmetrical hydrodynamical simulations to investigate the interaction of a collimated fast wind (CFW; wide jets) with a spherical AGB wind. The code includes radiative cooling. We find that the shape of the planetary nebula (PN) is sensitive to the exact mass loss history of the AGB wind, and the opening angle of the CFW. Some typical PN morphologies are obtained, but many other observed morphologies seem to require more ingredients than what we assume in our present simulations, e.g., equatorial AGB wind, and ionization and fast wind during the PN phase. The hot bipolar bubbl…
Long slit spectra of the molecular outflow Herbig-Haro (HH) 46/47 has been taken in the J and K near-infrared bands. The observed H2 line emission confirms the existence of a bright and extended redshifted counter-jet outflow southwest of HH46. We show that this outflow seems to be composed of two different emission regions which have distinct heliocentric velocities, in contrast with the optical appearance, and which implies an acceleration of the counter-jet. The observed [FeII] emission suggests an average extinction of 7-9 visual magnitudes for the region associated with the counter-jet. T…
We present deep Halpha+[N II] CCD images of selected new Planetary Nebulae (PNe) discovered through an [O III] 5007 A emission line survey in the Galactic Bulge region with l > 0 deg. In total, we detected more than 200 objects, including 45 new PNe. Deep Halpha+[N II] CCD images as well as low resolution spectra were obtained for the new PNe in order to study them in detail. Their first morphological study suggests that most of them are round (60%), while 31% and 9% are elliptical and bipolar, respectively. 63% of the round PNe present ring-like structure while 37% are compact.
We present near-IR spectroscopy of a sample of 30 IRAS sources recently identified as late AGB stars, post-AGB stars or early PNe. The spectra obtained are centered at various wavelengths covering the molecular hydrogen v=1-0 S(1) and v=2-1 S(1) emission lines, the recombination lines of hydrogen Br-gamma, Pf-gamma and Br-alpha, and the CO[v=2-0] first overtone bandhead at 2.294 microns. As a result of these observations we have increased from 4 to 13 the total number of proto-PNe detected in molecular hydrogen. When the molecular hydrogen is fluorescence-excited the detection rate is found to…
We present OH maser observations at 1612, 1665, 1667, and 1720 MHz for 86 post-asymptotic giant branch (post-AGB) stars selected from a survey of 1612 MHz maser sources in the Galactic Plane. The observations were taken with the Parkes Telescope and the Australia Telescope Compact Array between 2002 September and 2003 August. Post-AGB stars are the precursors to planetary nebulae, the diverse morphological range of which is unexplained. The maser observations were taken to investigate the onset and incidence of wind asymmetries during the post-AGB phase. We re-detected all 86 sources at 1612 M…
Some basic structures in planetary nebulae are modeled as self-organized magnetohydrodynamic (MHD) plasma configurations with radial flow. These configurations are described by time self-similar dynamics, where space and time dependences of each physical variable are in separable form. Axisymmetric toroidal MHD plasma configuration is solved under the gravitational field of a central star of mass $M$. With an azimuthal magnetic field, this self-similar MHD model provides an equatorial structure in the form of an axisymmetric torus with nested and closed toroidal magnetic field lines. In the ab…
We have constructed a grid of photoionization models of spherical, elliptical and bipolar planetary nebulae. Assuming different velocity fields, we have computed line profiles corresponding to different orientations, slit sizes and positions. The atlas is meant both for didactic purposes and for the interpretation of data on real nebulae. As an application, we have shown that line profiles are often degenerate, and that recovering the geometry and velocity field from observations requires lines from ions with different masses and different ionization potentials. We have also shown that the emp…
We use a 3D photoionization modeling tool to study the morpho-kinematic properties of the Planetary Nebula (PN) NGC 3132. We show that it is possible to reproduce the low resolution observations (spectra and images) with an ellipsoidal shell. However, high resolution observations, as those showing a density variation along the nebula and the [O III]5007 velocity profiles, definitively rule out this description. We show that a bipolar Diabolo shape with a 40 degres rotation of the symmetry axis relative to the line of sight successfully reproduces the observed images, as well as the high resolu…
Planetary Nebulae (PNe) are very important kinematical tracers of the outer regions of early-type galaxies, where the integrated light techniques fail. Under ad hoc assumptions, they allow measurements of rotation velocity and velocity dispersion profile from descrete radial velocity fields. We present the results on the precision allowed by different set of radial velocity samples, discuss the hypotheses in the analysis of descrete velocity fields and their impact on the inferred kinematics of the stellar population.
In this review I present the binary model for the shaping of planetary nebulae (PNe) as I view it, in the context of historical evolution of other models for the shaping of PNe over more than 30 years. In describing the binary model, I concentrate on works published since the last IAU meeting on PNe. I think stellar companions are behind the shaping of bipolar PNe, i.e., having two lobes with an equatorial waist between them, and extreme elliptical PNe, e.g., having a dense equatorial ring, but no lobes. The question of whether a planet is required to spin the progenitor in order to form a mod…
Using the Cloudy_3D code (Morisset, this conference), we run a set of models to build a catalog of emission line profiles of PNe. The goal is to cover the main morphologies (spherical, ellipsoidal, bipolar, thin or thick shells) and to compute profiles changing the orientation of the nebula, the expansion velocity law (including or not turbulence), the position/size of the aperture. The results is a huge set of profiles and PV-diagrams that can be compared to observations as a help to derive morpho-kinematical properties of real objects.
Type I planetary nebulae (PNe) are defined as those with high He and N abundances (Peimbert & Torres-Peimbert 1983). These objects present in general bipolar geometries and have high stellar temperatures (Corradi & Schwarz 1995, Torres-Peimbert & Peimbert 1997). In this paper we analyse the empirical methods for abundance determination in order to check if the He and N overabundances in Type I PNe are a consequence of a geometrical effect, due to the bipolarity, or the ionization stratification, due to the stellar temperature. For this, we obtain simulated spherically symmetrical as well as bi…
We present the results of ISO SWS and LWS grating scans towards the embedded Young Stellar Objects (YSOs) S106 IR and Cep A East. Emission from the pure rotational lines of H2 and the infrared fine structure lines of [C II], [O I], [S I], [Si II] and [Fe II], as well as absorption bands due to H2O, CO and CO2 ice were detected toward Cep A. In S106 we detected emission lines of H2, CO, H I, and a large number of ionized species including Fe, O, N, C, Si, S, Ne and Ar. S106 also shows many of the infrared PAH bands in emission. Excitation temperatures and molecular hydrogen masses were derived …
Planetary nebulae (PNe) exist in a range of different morphologies, from very simple and symmetric round shells, to elliptical, bipolar, and even quadrupolar shapes. They present extremely complex ensembles of filaments, knots, ansae, and shell multiplicity. It is then overwhelmingly complicated to derive reasonable evolutionary paths to justify the observed shapes of PNe. The confrontation between the evolution of the shells and that of the central stars is needed to understand the origin of the morphological variety. We present some background and recent results on the correlations between P…
High spatial resolution images of PNe have shown their extremely complex morphology. However, the circumstellar envelopes of their progenitors, the AGB stars, are strikingly spherical. In order to understand the carving processes leading to axisymmetric nebulae, we are carrying out a study of a large sample of pre-PNe. Our emission model of the nebular molecular gas (12CO & 13CO) will allow us to determine important physical parameters (mass, linear momentum, kinetic energy) of the fast bipolar and slow spherical nebular components separately. We will study in an innovative way the properties …
We present a spectroscopic investigation of two hitherto unstudied galactic planetary nebulae (MeWe 1-10 and MeWe 1-11) and one candidate object (MeWe 2-5). The candidate object clearly has been identified as a bipolar hourglass shaped PN. The galactic foreground extinction was derived and using photoionization models with CLOUDY the two round objects were classified as highly evolved nebulae.
