Knots in the Outer Shells of the Planetary Nebulae IC 2553 and NGC 5882

Corradi, R. L. M.; Gonçalves, Denise R.; Villaver, E.; Mampaso, A.; Perinotto, M.

doi:10.1086/317041

Cited by 25 publications

(32 citation statements)

References 23 publications

(29 reference statements)

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“…7, a set of NGC 5882 maps is presented showing the observed Hβ, the logarithmic extinction at Hβ, and a sample of representative dereddened spectral maps in the light of He i λ4471, He ii λ4686, [O iii ]λ4959, [Ne iii ]λ3967, and the recombination lines C ii λ4267 and O ii λ4649. The top two rows of the array appear very bright in the ‘unmasked’ Hβ image: this does not appear in images of the other two PNe [except perhaps in spaxels (3–5, 22) for the brightest emission lines of NGC 6153] and was judged to be a combination of the effects of differential atmospheric extinction at the edge of the field of view and the fact that the line flux there shows quite a steep gradient – this is also evident from a comparison of our line map with the HST F555W image of the PN which shows a confluence of clumped, relatively high surface brightness emission in that area (Corradi et al 2000). Such a gradient at the edge of the array could introduce errors in ratios of lines originating from the different LR02 and LR03 gratings and so these two rows were masked out and are not considered in the physical analysis of NGC 5882 that follows.…”

Section: Resultsmentioning

confidence: 89%

Integral field spectroscopy of planetary nebulae: mapping the line diagnostics and hydrogen-poor zones with VLT FLAMES

Tsamis

Walsh

Pequignot

et al. 2008

Monthly Notices of the Royal Astronomical Society

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Results from the first dedicated study of Galactic planetary nebulae (PNe) by means of optical integral field spectroscopy with the Very Large Telescope Fibre Large Array Multi Element Spectrograph Argus integral field unit are presented. Three typical Galactic disc PNe have been mapped with the 11.5 × 7.2‐arcsec2 Argus array: 2D spectral maps of the main shell of NGC 5882 and of large areas of NGC 6153 and NGC 7009 with 297 spatial pixels per target were obtained at subarcsec resolutions. A corresponding number of 297 spectra per target were obtained in the 396.4–507.8 nm range. Spatially resolved maps of emission lines and of nebular physical properties such as electron temperatures, densities and ionic abundances were produced. The abundances of helium and of doubly ionized carbon and oxygen, relative to hydrogen, were derived from optical recombination lines (ORLs), while those of O2+ were also derived from the classic collisionally excited lines (CELs). The occurrence of the abundance discrepancy problem, pertaining to oxygen, was investigated by mapping the ratio of ORL/CEL abundances for O2+[the abundance discrepancy factor (ADF)] across the face of the PNe. The ADF varies between targets and also with position within the targets, attaining values of ∼40 in the case of NGC 6153 and ∼30 in the case of NGC 7009. Correlations of the ADF with geometric distance from the central star and plasma surface brightness (for NGC 6153), as well as with [O iii] electron temperature, plasma ionization state and other physical properties of the targets are established. Very small values of the temperature fluctuation parameter in the plane of the sky, t2A(O2+), are found in all cases. It is argued that these results provide further evidence for the existence in run‐of‐the‐mill PNe of a distinct nebular component consisting of hydrogen‐deficient, super‐metal‐rich plasma. The zones containing this posited component appear as undulations in the C ii and O ii ORL abundance diagnostics of about 2 spatial pixels across, and so any associated structures should have physical sizes of less than ∼1000 astronomical units. Regarding the origin of the inferred zones, we propose that circumstellar discs, Abell 30‐type knots, or Helix‐type cometary globules may be involved. Implications for emission‐line studies of nebulae are discussed.

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Section: Resultsmentioning

confidence: 89%

Integral field spectroscopy of planetary nebulae: mapping the line diagnostics and hydrogen-poor zones with VLT FLAMES

Tsamis

Walsh

Pequignot

et al. 2008

Monthly Notices of the Royal Astronomical Society

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“…Mellema 1995;Corradi et al 2000;Villaver et al 2002), due to a Dtype ionization front in the early evolution of the PN. However, all these models fail to reproduce the smooth, innermost radial density profile observed in NGC 6818 (Fig.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

The 3-D ionization structure of NGC 6818: A Planetary Nebula threatened by recombination

Benetti

Ragazzoni

Sabbadin

et al. 2003

A&A

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Abstract. Long-slit NTT+EMMI echellograms of NGC 6818 (the Little Gem) at nine equally spaced position angles, reduced according to the 3-D methodology introduced by Sabbadin et al. (2000a,b), allowed us to derive: the expansion law, the diagnostics and ionic radial profiles, the distance and the central star parameters, the nebular photo-ionization model, the 3-D reconstruction in He II, [O III] and [N II], the multicolor projection and a series of movies. The Little Gem results to be a young (3500 years), optically thin (quasi-thin in some directions) double shell (M ion 0.13 M ) at a distance of 1.7 kpc, seen almost equatorial on: a tenuous and patchy spherical envelope (r 0.090 pc) encircles a dense and inhomogeneous tri-axial ellipsoid (a/2 0.077 pc, a/b 1.25, b/c 1.15) characterized by a hole along the major axis and a pair of equatorial, thick moustaches. NGC 6818 is at the start of the recombination phase following the luminosity decline of the 0.625 M central star, which has recently exhausted the hydrogen shell nuclear burning and is rapidly moving toward the white dwarf domain (log T * 5.22 K; log L * /L 3.1). The nebula is destined to become thicker and thicker, with an increasing fraction of neutral, dusty gas in the outermost layers. Only over some hundreds of years the plasma rarefaction due to the expansion will prevail against the slower and slower stellar decline, leading to a gradual re-growing of the ionization front. The exciting star of NGC 6818 (m V 17.06) is a visual binary: a faint, red companion (m V 17.73) appears at 0.09 arcsec in PA = 190 • , corresponding to a separation ≥150 AU and to an orbital period ≥1500 years.

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“…The technique uses the position on the sky and the measured radial velocity of the PN to infer a distance (e.g. Corradi & Schwarz 1993;Corradi et al 1997;Phillips 2001), assuming a model for the Galactic rotation curve. The approach can also be used for any neutral hydrogen in the foreground of the PN which causes an absorption line at 21 cm in the radio spectrum.…”

Section: Kinematic Distancesmentioning

confidence: 99%

The H surface brightness-radius relation: a robust statistical distance indicator for planetary nebulae

Frew¹,

Parker²,

Bojičić³

2015

Monthly Notices of the Royal Astronomical Society

169

127

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Measuring the distances to Galactic planetary nebulae (PNe) has been an intractable problem for many decades. We have now established a robust optical statistical distance indicator, the Hα surface brightness -radius or S Hα -r relation, which addresses this problem. We developed this relation from a critically evaluated sample of primary calibrating PNe. The robust nature of the method results from our revised calibrating distances with significantly reduced systematic uncertainties, and the recent availability of high-quality data, including updated nebular diameters and integrated Hα fluxes. The S Hα -r technique is simple in its application, requiring only an angular size, an integrated Hα flux, and the reddening to the PN. From these quantities, an intrinsic radius is calculated, which when combined with the angular size, yields the distance directly. Furthermore, we have found that optically thick PNe tend to populate the upper bound of the trend, while optically-thin PNe fall along the lower boundary in the S Hα -r plane. This enables sub-trends to be developed which offer even better precision in the determination of distances, as good as 18 per cent in the case of optically-thin, high-excitation PNe. This is significantly better than any previous statistical indicator. We use this technique to create a catalogue of statistical distances for over 1100 Galactic PNe, the largest such compilation in the literature to date. Finally, in an appendix, we investigate both a set of transitional PNe and a range of PN mimics in the S Hα -r plane, to demonstrate its use as a diagnostic tool. Interestingly, stellar ejecta around massive stars plot on a tight locus in S Hα -r space with the potential to act as a separate distance indicator for these objects.

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Knots in the Outer Shells of the Planetary Nebulae IC 2553 and NGC 5882

Cited by 25 publications

References 23 publications

Integral field spectroscopy of planetary nebulae: mapping the line diagnostics and hydrogen-poor zones with VLT FLAMES

Integral field spectroscopy of planetary nebulae: mapping the line diagnostics and hydrogen-poor zones with VLT FLAMES

The 3-D ionization structure of NGC 6818: A Planetary Nebula threatened by recombination

The H surface brightness-radius relation: a robust statistical distance indicator for planetary nebulae

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