Morphology and Kinematics of Planetary Nebulae. I. A New Modeling Tool (original) (raw)

Morphology and Kinematics of Planetary Nebulae. II. A Diabolo Model for NGC 3132

Astrophysical Journal, 2000

We present a new modeling tool for planetary nebulae, based on 3D photoionization calculations. Our goal is to show that all the information provided by observations, regarding kinematics and morphology, have to be consistently accounted for, in order to get a real insight of the object. Only 3D simulations offer this possibility. From models for two theoretical PNe, we show that the enhancement in the equatorial zone observed in several PNe is not necessarily due to a density gradient, as usually interpreted. It is also shown that asymmetric velocity profiles often observed (e.g., can be easily reproduced. Observations providing a better insight on the morphology of the PN are discussed.

Modelling of aspherical nebulae - I. A quick pseudo-3D photoionization code

Monthly Notices of The Royal Astronomical Society, 2005

We describe a pseudo-3D photoionization code, NEBU 3D and its associated visualization tool, VIS NEB3D, which are able to easily and rapidly treat a wide variety of nebular geometries, by combining models obtained with a 1D photoionization code. The only requirement for the code to work is that the ionization source is unique and not extended. It is applicable as long as the diffuse ionizing radiation field is not dominant and strongly inhomogeneous. As examples of the capabilities of these new tools, we consider two very different theoretical cases. One is that of a high excitation planetary nebula that has an ellipsoidal shape with two polar density knots. The other one is that of a blister HII region, for which we have also constructed a spherical model (the spherical impostor) which has exactly the same Hβ surface brightness distribution as the blister model and the same ionizing star.

3-D Photoionization Structure and Distances of Planetary Nebulae II. Menzel 1

2004

Continuing our series of papers on the three-dimensional (3D) structure and accurate distances of planetary nebulae (PNe), we present here the results obtained for PN NGC 40. Using data from different sources and wavelengths, we construct 3D photoionization models and derive the physical quantities of the ionizing source and nebular gas. The procedure, discussed in detail in the previous papers, consists of the use of 3D photoionization codes constrained by observational data to derive the 3D nebular structure, physical and chemical characteristics, and ionizing star parameters of the objects by simultaneously fitting the integrated line intensities, the density map, the temperature map, and the observed morphologies in different emission lines. For this particular case we combined hydrodynamical simulations with the photoionization scheme in order to obtain self-consistent distributions of density and velocity of the nebular material. Combining the velocity field with the emission-line cubes we also obtained the synthetic position-velocity plots that are compared to the observations. Finally, using theoretical evolutionary tracks of intermediate-and low-mass stars, we derive the mass and age of the central star of NGC 40 as (0.567 ± 0.06) M and (5810 ± 600) yr, respectively. The distance obtained from the fitting procedure was (1150 ± 120) pc.

Three-Dimensional Photoionization Structure and Distances of Planetary Nebulae. II. Menzel 1

Astrophysical Journal, 2005

3-D Photoionization Structure and Distances of Planetary Nebulae I. NGC6369

2004

Kinematics, turbulence and evolution of planetary nebulae

Astronomy and Astrophysics, 2003

This paper discusses the location of a sample of planetary nebulae on the HR diagram. We determine the internal velocity fields of 14 planetary nebulae from high-resolution echelle spectroscopy, with the help of photoionization models. The mass averaged velocity is shown to be a robust, simple parameter describing the outflow. The expansion velocity and radius are used to define the dynamical age; together with the stellar temperature, this gives a measurement of the luminosity and core mass of the central star. The same technique is applied to other planetary nebulae with previously measured expansion velocities, giving a total sample of 73 objects. The objects cluster closely around the Schönberner track of 0.61 Msun, with a very narrow distribution of core masses. The masses are higher than found for local white dwarfs. The luminosities determined in this way tend to be higher by a factor of a few than those derived from the nebular luminosities. The discrepancy is highest for the hottest (most evolved) stars. We suggest photon leakage as the likely cause. The innermost regions of the non-[WC] nebulae tend to show strong acceleration. Together with the acceleration at the ionization front, the velocity field becomes ``U''-shaped. The presence of strong turbulent motions in [WC] nebulae is confirmed. Except for this, we find that the [WC] stars evolve on the same tracks as non-[WC] stars. Based on observations taken at the ESO. Appendix A is only available in electronic form at http://www.edpsciences.org

Photoionization models of Planetary Nebulae

Proceedings of the International Astronomical Union, 2016

The understanding of astronomical nebulae is based on observational data (images, spectra, 3D data-cubes) and theoretical models. In this review, I present my very biased view on photoionization modeling of planetary nebulae, focusing on 1D multi-component models, on 3D models and on big database of models.

From bipolar to elliptical: simulating the morphological evolution of planetary nebulae

Monthly Notices of the Royal Astronomical Society, 2012

In this paper we model the evolution of PrePlanetary Nebula (PPN) and Planetary Nebula (PN) morphologies as a function of nebular age. The aim of the work is to understand if shape transitions from one evolutionary phase to the other can be driven by changes in the parameters of the mass-loss from the central star. We carry out 2.5D hydrodynamical simulations of mass-loss at the end stages of stellar evolution for intermediate mass stars. Changes in wind velocity, mass-loss rate and mass-loss geometry are tracked. We focus on the transition from mass-loss dominated by a short duration jet flow (driven during the PPN phase) to mass-loss driven by a spherical fast wind (produced by the central star of the PN). Our results show that while jet driven nebulae can be expected to be dominated by bipolar morphologies, systems that begin with a jet but are followed by a spherical fast wind will evolve into elliptical objects. Systems that begin with an aspherical AGB wind evolve into butterfly shaped nebula with, or without, a jet phase. In addition, our models show that spherical nebulae are highly unlikely to derive from either bipolar PPN or elliptical PN over relevant time scales. The morphological transitions seen in our simulations may however provide insight into the driving mechanisms of both PPN and PN as point to evolutionary changes in the central engine.

Evolution of planetary nebulae

Astronomy & Astrophysics, 2001

We present a new synthetic model to follow the evolution of a planetary nebula (PN) and its central star, starting from the onset of AGB phase up to the white dwarf cooling sequence. The model suitably combines various analytical prescriptions to account for different (but interrelated) aspects of planetary nebulae, such as: the dynamical evolution of the primary shell and surrounding ejecta, the photoionisation of H and He by the central star, the nebular emission of a few relevant optical lines (e.g. Hβ; He ii λ4686; [O iii] λ5007). Particular effort has been put into the analytical description of dynamical effects such as the three-winds interaction and the shell thickening due to ionisation (i.e. the thin-shell approximation is relaxed), that are nowadays considered important aspects of the PN evolution. Predictions of the synthetic model are tested by comparison with both findings of hydrodynamical calculations, and observations of Galactic PNe. The sensitiveness of the results to the model parameters (e.g. transition time, mass of the central star, H-/He-burning tracks, etc.) is also discussed. We briefly illustrate the systematic differences that are expected in the luminosities and lifetimes of PNe with either H-or He-burning central stars, which result in different "detection probabilities" across the H-R diagram, in both Hβ and [Oiii] λ5007 lines. Adopting reasonable values of the model parameters, we are able to reproduce, in a satisfactory way, many general properties of PNe, like the ionised mass-nebular radius relationship, the trends of a few main nebular line ratios, and the observed ranges of nebular shell thicknesses, electron densities, and expansion velocities. The models naturally predict also the possible transitions from optically-thick to optically-thin configurations (and vice versa). In this context, our analysis indicates that the condition of optical thinness to the H continuum plays an important role in producing the observed "Zanstra discrepancy" between the temperatures determined from H or He ii lines, as well as it affects the mass-increasing part of the ionised mass-radius relation. These predictions are supported by observational indications by Méndez et al. (1992). Another interesting result is that the change of slope in the electron density-nebular radius relation at Rion ∼ 0.1 pc, pointed out by Phillips (1998), is also displayed by the models and may be interpreted as the result of the progressive convergence of the PNe to the condition of constant ionised mass. Finally we would like to remark that, thanks to its computational agility, our synthetic PN model is particularly suitable to population synthesis studies, and it represents the basic ground from which many future applications will be developed.

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.

Morphology and Kinematics of Planetary Nebulae. I. A New Modeling Tool (original) (raw)

Related papers