Rings and arcs around evolved stars – III. Physical conditions of the ring-like structures in the planetary nebula IC 4406 revealed by MUSE

We present the analysis of Very Large Telescope Multi Unit Spectroscopic Explorer (MUSE) observations of the planetary nebula (PN) IC 4406. MUSE images in key emission lines are used to unveil the presence of at least five ring-like structures north and south of the main nebula of IC 4406. MUSE spectra are extracted from the rings to unambiguously assess for the first time in a PN their physical conditions, electron density (ne), and temperature (Te). The rings are found to have similar Te as the rim of the main nebula, but smaller ne. Ratios between different ionic species suggest that the rings of IC 4406 have a lower ionization state than the main cavity, in contrast to what was suggested for the rings in NGC 6543, the Cat’s Eye Nebula. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
GR-L acknowledges support from CONACyT grant 263373 and PRODEP (Mexico). VMAGG acknowledges support from the Programa de Becas posdoctorales of the Dirección General de Asuntos del Personal Académico (DGAPA) of the Universidad Nacional Autónoma de México (UNAM, Mexico). VMAGG and JAT acknowledge funding by DGAPA UNAM PAPIIT project IA100720. JAT also acknowledges support from the Marcos Moshinsky Fundation (Mexico). JBR-G thanks CONACyT for a student scholarship. MAG acknowledges support of the Spanish Ministerio de Ciencia, Innovación y Universidades grant PGC2018-102184-B-I00, co-funded by FEDER funds. Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA). Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO programme 60.A-9100. Based on observations obtained at the Canada–France–Hawaii Telescope (CFHT). This work has made extensive use of the NASA’s Astrophysics Data System.