Fig 9 - uploaded by Christophe Morisset
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A 3D map of the bipolar nebula model from Sec. 3.1. Each quadrant corresponds to a different emission line. The surface brightness is represented by levels of grey. Superimposed on this image are the profiles of the same lines, integrated over areas of 5x5 pixels.
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Presentamos una herramienta, VELNEB 3D, que puede ser aplicada a resultados de códigos de fotoionización 1D o 3D para generar perfiles de líneas de emisión, mapas posición-velocidad y mapas 3D en cualquier línea de emisión suponiendo un campo de velocidad arbitrario. Presentamos algunos ejemplos, basados en nuestro
pseudo-3D código de fotoionizació...
Context in source publication
Context 1
... (or velocity) being the third dimension. Such examples can be found in Ambrocio-Cruz, Laval, Rosado, Georgelin, Marcelin, Comeron, Delmotte & Viale (2004); Vasconcelos, Cerqueira, Plana, Raga & Morisset (2005). Our tool is well-suited to also produce such maps for photoionization models of asymmetric nebulae. One such example is shown in Fig. 9, which represents the bipolar nebula model from Sec. 3.1. Each quadrant corresponds to a different emission line (Hβ, He II 4689Å4689Å, [N II] 6583Å6583Å, and [O III] 5007Å5007Å). The grey-colour image represents the surface brightness in the line, computed with pixels of 0.075 ′′ x 0.075 ′′ . Superimposed on this image are the ...
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Introduction Emission lines are observed almost everywhere in the Universe, from the Earth's atmosphere (see Wyse & Gilmore 1992 for a summary) to the most-distant objects known (quasars and galaxies), on all scales and at all wavelengths, from the radio domain (e.g. Lobanov 2005) to gamma rays (e.g. Diehl et al. 2006). They provide very efficient tools to explore the Universe, measure the chemical composition of celestial bodies and determine the physical conditions prevailing in the regions where they are emitted. The subject is extremely vast. Here, we will restrict ourselves in wavelength, being mostly concerned with the optical domain, with some excursions to the infrared and ultraviolet domains and, occasionally, to the X-ray region. We will mainly deal with the mechanisms of line production and with the interpretation of line intensities in various astrophysical contexts. We will discuss neither quasars and Seyfert galaxies, since those are the subject of Chapter 5, nor Lyman-α galaxies, which are extensively covered in Chapter 4 of this book. However, we will discuss diagnostic diagrams used to distinguish active galaxies from other emission-line galaxies and will mention some topics linked with H Lyα. Most of our examples will be taken from recent literature on planetary nebulae, H II regions and emission-line galaxies. Emission-line stars are briefly described in Chapter 7 and a more detailed presentation is given in the book The Astrophysics of Emission Line Stars by Kogure & Leung (2007).
We compare calculated intensities of lines of C ii, N i, N ii, O i and O ii with a published deep spectroscopic survey of IC 418. Our calculations use a self-consistent nebular model and a synthetic
spectrum of the central star atmosphere to take into account line excitation by continuum fluorescence and electron recombination.
We found that the N ii spectrum of the s, p and most d states is excited by fluorescence due to the low-excitation conditions of the nebula. Many
C ii and O ii lines have significant amount of excitation by fluorescence. Recombination excites all the lines from the f and g states
and most O ii lines. In the neutral-ionized boundary, the N i quartet and O i triplet dipole-allowed lines are excited by fluorescence, while the quintet O i lines are excited by recombination. Electron excitation produces the forbidden optical lines of O i, and continuum fluorescence enhances the N i forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to
explore the inner boundary of the photodissociation region of the nebula.
We predict intensities of lines of CII, NI, NII, OI and OII and compare them
with a deep spectroscopic survey of IC 418 to test the effect of excitation of
nebular emission lines by continuum fluorescence of starlight. Our calculations
use a nebular model and a synthetic spectrum of its central star to take into
account excitation of the lines by continuum fluorescence and recombination.
The NII spectrum is mostly produced by fluorescence due to the low excitation
conditions of the nebula, but many CII and OII lines have more excitation by
fluorescence than recombination. In the neutral envelope, the NI permitted
lines are excited by fluorescence, and almost all the OI lines are excited by
recombination. Electron excitation produces the forbidden optical lines of OI,
but continuum fluorescence excites most of the NI forbidden line intensities.
Lines excited by fluorescence of light below the Lyman limit thus suggest a new
diagnostic to explore the photodissociation region of a nebula.
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 empirical way to measure mass-weighted expansion velocities from observed line widths is reasonably accurate if considering the HWHM. For distant nebulae, entirely covered by the slit, the unknown geometry and orientation do not alter the measured velocities statistically. The atlas is freely accessible from internet. The Cloudy 3D suite and the associated VISNEB tool are available on request.
We present an analysis of physical conditions in planetary nebulae (PNe) in terms of collisionally-excited line (CEL) and optical-recombination line (ORL) profiles. We aim to investigate whether line profiles could be used to study the long-standing CEL/ORL abundance-discrepancy problem in nebular astrophysics. Using 1D photoionization models and their assumed velocity fields, we simulate the line profiles of various ionic species. We attempt to use our model to account for the observed CEL and ORL profiles. As a case study we present a detailed study of line profiles of the low-excitation planetary nebula (PN) IC 418. Our results show that the profiles of classical temperature and density diagnostic lines, such as [O III] 4363,5007, [S II] 6716,6731, and [Ar IV] 4711,4740, provide a powerful tool to study nebular temperature and density variations. The method enables the CEL/ORL abundance-discrepancy problem to be studied more rigorously than before. A pure photoionization model of a chemically-homogeneous nebula seems to explain the observed disagreements in the profiles for the [O III] 4363 and the 5007 lines, but cannot account for the differences between the [O III] CELs and the O II ORLs. We also investigate the temperature and density variations in the velocity space of a sample of PNe, which are found to be insignificant. Comment: 9 pages, 10 figures, Accepted for publication in A&A
We developed a new quick pseudo-3D photoionization code based on Cloudy (G. Ferland) and IDL (RSI) tools. The code is running the 1D photoionization code Cloudy various times, changing at each run the input parameters (e.g. inner radius, density law) according to an angular law describing the morphology of the object. Then a cube is generated by interpolating the outputs of Cloudy. In each cell of the cube, the physical conditions (electron temperature and density, ionic fractions) and the emissivities of lines are determined. Associated tools (VISNEB and VELNEB_3D) are used to rotate the nebula and to compute surface brightness maps and emission line profiles, given a velocity law and taking into account the effect of the thermal broadening and eventually the turbulence. Integrated emission line profiles are computed, given aperture shapes and positions (seeing and instrumental width effects are included). The main advantage of this tool is the short time needed to compute a model (a few tens minutes). Comment: To appear in Proc. IAU Symp. 234, Planetary Nebulae in Our Galaxy and Beyond (3-7 Apr 2006), eds. M.J. Barlow & R.H. Mendez (Cambridge Univ. Press)
