eprintid: 10095990
rev_number: 16
eprint_status: archive
userid: 608
dir: disk0/10/09/59/90
datestamp: 2020-09-22 16:09:02
lastmod: 2021-10-11 22:27:29
status_changed: 2020-09-22 16:09:02
type: article
metadata_visibility: show
creators_name: Ercolano, B
creators_name: Wesson, R
creators_name: Zhang, Y
creators_name: Barlow, MJ
creators_name: De Marco, O
creators_name: Rauch, T
creators_name: Liu, XW
title: Observations and three-dimensional photoionization modelling of the Wolf-Rayet planetary nebula NGC 1501
ispublished: pub
divisions: UCL
divisions: B04
divisions: C06
divisions: F60
keywords: atomic data, stars : Wolf-Rayet, ISM : abundances, planetary nebulae : individual : NGC 1501
note: This version is the version of record. For information on re-use, please refer to the publisher's terms and conditions.
abstract: Deep optical spectra of the high‐excitation planetary nebula NGC 1501 and its W04 central star are presented. A recombination line abundance analysis of the emission‐line spectrum of the central star yields He : C : O mass fractions of 0.36 : 0.48 : 0.16, similar to those of PG 1159 stars. A detailed empirical analysis of the nebular collisionally excited line (CEL) and optical recombination line (ORL) spectrums are presented, together with fully three‐dimensional photoionization modelling of the nebula. We found very large ORL–CEL abundance discrepancy factors (ADFs) for O^{2+} (32) and Ne^{2+} (33). The mean value of ∼5100 K for the T_{e} derived from He I recombination lines ratios is 6000 K, lower than the value of 11 100 K implied by the [O III] line ratio. This result indicates the existence of a second, low-temperature nebular component, which could account for the observed ORL emission. Electron temperature
fluctuations (t^{2}) cannot account for the high ADFs found from our optical spectra of this nebula. A three‐dimensional photoionization model of NGC 1501 was constructed using the photoionization code_{mocassin}, based on our new spectroscopic data and using the three‐dimensional electron density distribution determined from long‐slit echellograms of the nebula by Ragazzoni et al. The central star ionizing radiation field is approximated by a model atmosphere, calculated using the Tübingen non‐local thermodynamic equilibrium model atmosphere package, for abundances typical of the W04 nucleus of NGC 1501 and PG 1159 stars. The nebular emission‐line spectrum was best reproduced using a central star model with an effective temperature of Teff= 110 kK and a luminosity of L_{*}= 5000 L_{⊙}. The initial models showed higher degrees of ionization of heavy elements than indicated by observations. We investigated the importance of the missing low‐temperature dielectronic recombination rates for third‐row elements and have estimated upper limits to their rate coefficients.

Our single‐phase, three‐dimensional photoionization model heavily underpredicts the optical recombination line emission. We conclude that the presence of a hydrogen‐deficient, metal‐rich component is necessary to explain the observed ORL spectrum of this object. The existence of such knots could also provide a softening of the radiation field, via the removal of ionizing photons by absorption in the knots, thereby helping to alleviate the overionization of the heavy elements in our models.
date: 2004-10
date_type: published
publisher: OXFORD UNIV PRESS
official_url: https://doi.org/10.1111/j.1365-2966.2004.08218.x
oa_status: green
full_text_type: pub
language: eng
primo: open
primo_central: open_green
verified: verified_manual
elements_id: 137579
doi: 10.1111/j.1365-2966.2004.08218.x
lyricists_name: Barlow, Michael
lyricists_name: Wesson, Roger
lyricists_id: MJBAR75
lyricists_id: RWESS64
actors_name: Barlow, Michael
actors_id: MJBAR75
actors_role: owner
full_text_status: public
publication: Monthly Notices of the Royal Astronomical Society
volume: 354
number: 2
pagerange: 558-574
pages: 17
citation:        Ercolano, B;    Wesson, R;    Zhang, Y;    Barlow, MJ;    De Marco, O;    Rauch, T;    Liu, XW;      (2004)    Observations and three-dimensional photoionization modelling of the Wolf-Rayet planetary nebula NGC 1501.                   Monthly Notices of the Royal Astronomical Society , 354  (2)   pp. 558-574.    10.1111/j.1365-2966.2004.08218.x <https://doi.org/10.1111/j.1365-2966.2004.08218.x>.       Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/10095990/1/ercolano_ngc1501.pdf