The correlation between expansion velocity and morphology   in planetary nebulae

Phillips, J. P.

doi:10.1051/0004-6361:20020883

Cited by 10 publications

(16 citation statements)

References 18 publications

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“…Phillips & Mampaso 1988; Phillips & Ramos‐Larios 2008a). Similarly, observed gas outflow velocities are of the order of 18.2 ± 1.1 km s −1 – a value at the lower end of the planetary nebula range; spherical nebulae, for instance, have values V EXP ≅ 24.8 ± 1 km s −1 (Phillips 2002). The wings of the lines often show velocities extending up to ∼370 km s −1 , however (Corradi & Schwarz 1995).…”

Section: Introductionmentioning

confidence: 93%

Spitzer mid-infrared observations of seven bipolar planetary nebulae

Phillips¹,

Ramos-Larios²

2010

Monthly Notices of the Royal Astronomical Society

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We have investigated the mid‐infrared (MIR) and visual structures of seven bipolar planetary nebulae (BPNe), using imaging and spectroscopy acquired using the Spitzer Space Telescope (SST), and the Observatorio Astronomico Nacional in Mexico. The results show that the sources are more extended towards longer MIR wavelengths, as well as having higher levels of surface brightness in the 5.8‐ and 8.0‐μm bands. It is also noted that the 5.8 μm/4.5 μm and 8.0 μm/4.5 μm flux ratios increase with increasing distance from the nuclei of the sources. All of these latter trends may be attributable to emission by polycyclic aromatic hydrocarbons (PAHs) and/or warm dust continua within circumnebular photodissociation regions (PDRs). A corresponding decrease in the flux ratios 8.0 μm/5.8 μm may, by contrast, arise due to changes in the properties of the PAH emitting grains. We note evidence for 8.0 μm ring‐like structures in the envelope of NGC 2346, located in a region beyond the minor axis limits of the ionized envelope. An analysis of the inner two rings shows that whilst they have higher surface brightnesses at longer MIR wavelengths, they are relatively stronger (compared to underlying emission) at 3.6 and 4.5 μm. There is also evidence for point‐reflection symmetry along the major axis of the outflow. Finally, the fall‐off in surface brightness along the nebular minor axis suggests that progenitor mass‐loss rates were more‐or‐less constant. NGC 6905 shows evidence for a centrally located and unresolved MIR emission excess. We show that whilst flux ratios are inconsistent with stellar and ionized gas components of emission, the emission can be explained in terms of shock‐excited H2, or grain continuum and PAH emission bands. We provide the deepest image so far published of the outer visual structure of NGC 6445, and compare these results with Spitzer imaging at 8.0 μm. The distributions are quite distinct, and may indicate collimation of the outer ionized emission by a cylindrical PDR. We finally note that the MIR colours of the lobes and nuclei of the sources are radically different. It is also shown that 3.6‐μm emission in BPNe differs from that for the generality of planetary nebulae. We discuss various mechanisms which may contribute to these differences of colour.

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Section: Introductionmentioning

confidence: 93%

Spitzer mid-infrared observations of seven bipolar planetary nebulae

Phillips¹,

Ramos-Larios²

2010

Monthly Notices of the Royal Astronomical Society

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“…It also appears that the diameters of the BPNe refer primarily to the bright cores of these sources, rather than the more extended nebular lobes. Phillips (2003b) has shown that such cores are probably similar in size to the envelopes of circular and elliptical PNe, given similar levels of surface brightness, and that their velocities of expansion are also comparable (Phillips 2002a). These various morphological types (i.e.…”

Section: Properties Of the Observed Zanstra Temperaturesmentioning

confidence: 99%

“…This is consistent with the mean trends in latitude cited above, and suggests that elliptical sources are associated with a large range of progenitor masses. Similarly, there appear to be small but significant variations in the velocities of expansion of the sources (Phillips 2002a), although their dimensions are similar where brightness temperatures are comparable (Phillips 2003b).…”

Section: Introductionmentioning

confidence: 99%

The relation between Zanstra temperature and morphology in planetary nebulae

Phillips¹

2003

Monthly Notices RAS

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We have created a master list of Zanstra temperatures for 373 galactic planetary nebulae based upon a compilation of 1575 values taken from the published literature. These are used to evaluate mean trends in temperature for differing nebular morphologies. Among the most prominent results of this analysis is the tendency for η=TZ(He ii)/TZ(He i) to increase with nebular radius, a trend which is taken to arise from the evolution of shell optical depths. We find that as many as 87 per cent of nebulae may be optically thin to H ionizing radiation where radii exceed ∼0.16 pc. We also note that the distributions of values η and TZ(He ii) are quite different for circular, elliptical and bipolar nebulae. A comparison of observed temperatures with theoretical H‐burning tracks suggests that elliptical and circular sources arise from progenitors with mean mass 〈MPG〉≅ 1 M⊙ (although the elliptical progenitors are probably more massive). Higher‐temperature elliptical sources are likely to derive from progenitors with mass ≅2 M⊙, however, implying that these nebulae (at least) are associated with a broad swathe of progenitor masses. Such a conclusion is also supported by trends in mean galactic latitude. It is found that higher‐temperature elliptical sources have much lower mean latitudes 〈b〉 than those with smaller TZ(He ii), a trend which is explicable where there is an increase in 〈MPG〉 with increasing TZ(He ii). This latitude–temperature variation also applies for most other sources. Bipolar nebulae appear to have mean progenitor masses ≅2.5 M⊙, whilst jets, Brets and other highly collimated outflows are associated with progenitors at the other end of the mass range (〈MPG〉∼ 1 M⊙). Indeed it is possible, given their large mean latitudes and low peak temperatures, that the latter nebulae are associated with the lowest‐mass progenitors of all. The present results appear fully consistent with earlier analyses based upon nebular scale heights, shell abundances and the relative proportions of differing morphologies, and offer further evidence for a link between progenitor mass and morphology.

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“…This is supported by the evidence of shell expansion in Magellanic Cloud planetaries (Stanghellini et al 1999), and the invariance of observed expansion velocities V EXP with nebular radius (Phillips 2003d). Although there are systematic differences in velocity between the differing shell morphologies, these appear to be small (Phillips 2002a). Finally, we note that hydrodynamical models of expansion imply both acceleration and deceleration of the I-fronts (see e.g.…”

Section: The Expected Relation Between Brightness Temperature and Mormentioning

confidence: 72%

The correlation between planetary nebula morphology and radio brightness temperatures

Phillips¹

2003

A&A

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Abstract. We have used model central star evolutionary tracks to evaluate the expected variation of 5 GHz brightness temperatures T B in planetary nebulae. Using these results, and previously derived central star mass functions, we find that there should be a correlation between T B and the mean central star mass M CS , and also between T B and nebular morphology. An analysis of the available observational results suggests that such a correlation between T B and nebular morphology does indeed exist. Bipolar nebulae appear to be concentrated towards high brightness temperatures, whilst circular sources tend to possess lower brightness temperature shells. Elliptical sources are present (and common) at all values of T B . There are differences however between the observed and deduced morphological variations, and these enable us to place constraints upon the progenitor masses of the nebulae. In particular, it is clear that higher mass progenitors are likely to give rise to both bipolar and elliptical outflows; a result which is consistent with analyses of nebular abundances, Zanstra temperatures, and line excitations.

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The correlation between expansion velocity and morphology in planetary nebulae

Cited by 10 publications

References 18 publications

Spitzer mid-infrared observations of seven bipolar planetary nebulae

Spitzer mid-infrared observations of seven bipolar planetary nebulae

The relation between Zanstra temperature and morphology in planetary nebulae

The correlation between planetary nebula morphology and radio brightness temperatures

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