MUSE spectroscopy of the high abundance discrepancy planetary nebula NGC 6153

¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
² Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
³ Instituto de Astronomía (IA), Universidad Nacional Autónoma de México, Apdo. postal 106, C.P. 22800 Ensenada, Baja California, Mexico
⁴ Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad s/n, 62210 Cuernavaca, Mor., Mexico
⁵ Instituto de Física e Química, Universidade Federal de Itajubá, Av. BPS 1303-Pinheirinho, 37500-903, Itajubá, Brazil
⁶ Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, 38711 Breña Baja, Spain
⁷ School of Physics and Astronomy, Cardiff University, Queen’s Buildings, The Parade, Cardiff CF24 3AA, UK
⁸ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85738 Garching bei München, Germany
⁹ Gran Telescopio CANARIAS S.A., c/ Cuesta de San José s/n, Breña Baja, 38712 Santa Cruz de Tenerife, Spain

Received: 22 May 2024
Accepted: 16 July 2024

Abstract

Context. The abundance discrepancy problem in planetary nebulae (PNe) has long puzzled astronomers. NGC 6153, with its high abundance discrepancy factor (ADF ~ 10), provides a unique opportunity to study the chemical structure and ionisation processes within these objects.

Aims. We aim to understand the chemical structure and ionisation processes in this high-ADF nebula by constructing detailed emission line maps and examining variations in electron temperature and density. This study also explores the discrepancies between ionic abundances derived from collisional and recombination lines, shedding light on the presence of multiple plasma components.

Methods. We used the MUSE spectrograph to acquire IFU data covering the wavelength range 4600–9300 Å with a spatial sampling of 0.2 arcsec and spectral resolutions ranging from R = 1609 to R = 3506. We created emission line maps for 60 lines and two continuum regions. We developed a tailored methodology for the analysis of the data, including correction for recombination contributions to auroral lines and the contributions of different plasma phases.

Results. Our analysis confirmed the presence of a low-temperature plasma component in NGC 6153. We find that electron temperatures derived from recombination line and continuum diagnostics are significantly lower than those derived from collisionally excited line diagnostics. Ionic chemical abundance maps were constructed, considering the weight of the cold plasma phase in the H I emission. Adopting this approach we found ionic abundances that could be up to 0.2 dex lower for those derived from CELs and up to 1.1 dex higher for those derived from RLs than in the case of a homogeneous H I emission. The abundance contrast factor (ACF) between both plasma components was defined, with values, on average, 0.9 dex higher than the ADF. Different methods for calculating ionisation correction factors (ICFs), including state-of-the-art literature ICFs and machine learning techniques, yielded consistent results.

Conclusions. Our findings emphasise that accurate chemical abundance determinations in high-ADF PNe must account for multiple plasma phases. Future research should focus on expanding this methodology to a broader sample of PNe, with spectra deep enough to gather physical condition information of both plasma components, which will enhance our understanding of their chemical compositions and the underlying physical processes in these complex objects.