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Title:
Integral field spectroscopy of planetary nebulae: mapping the line diagnostics and hydrogen-poor zones with VLT FLAMES
Authors:
Tsamis, Y. G.; Walsh, J. R.; Péquignot, D.; Barlow, M. J.; Danziger, I. J.; Liu, X.-W.
Affiliation:
AA(Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT; Space Telescope European Co-ordinating Facility, European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching, Germany), AB(Space Telescope European Co-ordinating Facility, European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching, Germany), AC(LUTH, Observatoire de Paris, CNRS, Université Paris Diderot; 5 Place Jules Janssen, 92190 Meudon, France), AD(Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT), AE(Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34131 Trieste, Italy), AF(Department of Astronomy, Peking University, Beijing 100871, China)
Publication:
Monthly Notices of the Royal Astronomical Society, Volume 386, Issue 1, pp. 22-46. (MNRAS Homepage)
Publication Date:
05/2008
Origin:
MNRAS
MNRAS Keywords:
ISM: abundances , planetary nebulae: general , planetary nebulae: individual: NGC 5882 , planetary nebulae: individual: NGC 6153 , planetary nebulae: individual: NGC 7009
DOI:
10.1111/j.1365-2966.2008.13051.x
Bibliographic Code:
2008MNRAS.386...22T

Abstract

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 NGC5882 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 396.4-507.8nm 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 [OIII] 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 CII and OII 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.

Based on observations made with ESO telescopes at the Paranal Observatory under programme ID 075.D-0847(A).

E-mail: ygt@star.ucl.ac.uk

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