Volume 620, December 2018
|Number of page(s)||25|
|Section||Interstellar and circumstellar matter|
|Published online||14 December 2018|
European Southern Observatory, Karl-Schwarzschild Strasse 2,
2 Instituto de Astrofísica de Canarias (IAC), 38025 La Laguna, Tenerife, Spain
3 Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
4 Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
5 Department of Physics and Astronomy, University of Denver, 2112 E. Wesley Ave., Denver, CO, 80210, USA
6 Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Manchester M13 9PL, UK
7 Laboratory for Space Research, University of Hong Kong, Pokfulam Road, Hong Kong
8 Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile
9 Institut für Astro- und Teilchenphysik, Leopold–Franzens Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
10 Leiden Observatory, University of Leiden, Leiden, the Netherlands
11 Oberkasseler Straße 130, 40545 Düsseldorf, Germany
12 Okayama Observatory, Kyoto University Honjo, Kamogata, Asakuchi, Okayama, 719-0232, Japan
Accepted: 14 September 2018
Aims. The spatial structure of the emission lines and continuum over the 50″ extent of the nearby, O-rich, PN NGC 7009 (Saturn Nebula) have been observed with the MUSE integral field spectrograph on the ESO Very Large Telescope. This study concentrates on maps of line emission and their interpretation in terms of physical conditions.
Methods. MUSE Science Verification data, in <0.6″ seeing, have been reduced and analysed as maps of emission lines and continuum over the wavelength range 4750–9350 Å. The dust extinction, the electron densities and temperatures of various phases of the ionized gas, abundances of species from low to high ionization and some total abundances are determined using standard techniques.
Results. Emission line maps over the bright shells are presented, from neutral to the highest ionization available (He II and [Mn V]). For collisionally excited lines (CELs), maps of electron temperature (Te from [N II] and [S III]) and density (Ne from [S II] and [Cl III]) are available and for optical recombination lines (ORLs) temperature (from the Paschen jump and ratio of He I lines) and density (from high Paschen lines). These estimates are compared: for the first time, maps of the differences in CEL and ORL Te’s have been derived, and correspondingly a map of t2 between a CEL and ORL temperature, showing considerable detail. Total abundances of only He and O were formed, the latter using three ionization correction factors. However, the map of He/H is not flat, departing by ~2% from a constant value, with remnants corresponding to ionization structures. An integrated spectrum over an area of 2340 arcsec2 was also formed and compared to 1D photoionization models.
Conclusions. The spatial variation of a range of nebular parameters illustrates the complexity of the ionized media in NGC 7009. These MUSE data are very rich with detections of hundreds of lines over areas of hundreds of arcsec2 and follow-on studies are outlined.
Key words: planetary nebulae: individual: NGC 7009 / stars: AGB and post-AGB / ISM: abundances / dust, extinction / atomic processes
Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile in Science Verification (SV) observing proposal 60.A-9347(A).
FITS files of all the individual maps are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/620/A169
© ESO 2018
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