Hostname: page-component-54dcc4c588-mz6gc Total loading time: 0 Render date: 2025-10-07T15:20:02.640Z Has data issue: false hasContentIssue false
  • English
  • Français

What do we really know about the low-ionization structures in planetary nebulae?

Published online by Cambridge University Press:  06 October 2025

Stavros Akras Open the ORCID record for Stavros Akras [Opens in a new window]
Stavros Akras*
Affiliation:
Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, GR 15236 Penteli, Greece
*
Email: stavrosakras@gmail.com
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We do know that planetary nebulae (PNe) are ionized gaseous clouds of material ejected by evolved dying stars. The intense ultraviolet radiation field of these stars leads to the dissociation of the cold molecular gas and then to the ionization/excitation of the resultant atomic gas. The chemical composition, ionization structure, physical conditions and formation process of nebular shells, rims, and halos are well comprehended. On the contrary, the origin of low-ionization structures (LISs) frequently found in PNe break the overall picture, and it still remains poorly understood. The latest discoveries of molecular hydrogen (H2) in LISs have changed how we think about their origin. Besides the detection of H2 emission, the [Fe ii] 1.644μm and [C i] 8727Å lines have also been detected in LISs. These results add new pieces to the puzzling problem of LISs opening a new window to enrich our knowledge and understanding on these microstructures.

Keywords

(ISM:) planetary nebulae: generalISM: atomsISM: moleculesplanetary nebulae(ISM:) dustextinction

Information

Type
Contributed Paper
Information
Proceedings of the International Astronomical Union , Volume 19 , Symposium S384: Planetary Nebulae: A Universal Toolbox in the Era of Precision Astrophysics , December 2023 , pp. 163 - 169
Check for updates
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of International Astronomical Union

References

Akras, S., Gonçalves, D. R., 2016, MNRAS, 455, 930A CrossRefGoogle Scholar
Akras, S., Gonçalves, D. R., Ramos-Larios, G., 2017, MNRAS, 465, 1289A CrossRefGoogle Scholar
Akras, S., Gonçalves, D. R., Ramos-Larios, G., Aleman, I., 2020, MNRAS, 493, 3800A CrossRefGoogle Scholar
Akras, S., et al., 2022, MNRAS, 512, 2202A CrossRefGoogle Scholar
Balick, B., 1987, AJ, 94, 671B CrossRefGoogle Scholar
Balick, B., Rugers, M., Terzian, Y., et al., 1993, ApJ, 411, 778 CrossRefGoogle Scholar
Balick, B., Alexander, J., Hajian, A. R., et al., 1998, AJ, 116, 360B CrossRefGoogle Scholar
Balick, B., et al., 2020, ApJ, 889, 13 CrossRefGoogle Scholar
Black, J. H., van Dishoeck, E. F., 1987, ApJ, 322, 412 CrossRefGoogle Scholar
Burton, M. G., Hollenbach, D. J., Tielens, A. G. G. M., 1990, ApJ, 365, 620B CrossRefGoogle Scholar
Burton, M. G., Bulmer, M., Moorhouse, A., et al., 1992, MNRAS, 257, 1P CrossRefGoogle Scholar
Decin, L., 2021, ARA&A, 59, 337D Google Scholar
De Marco, O., Akashi, M., Akras, S., et al., 2022, NatA, 6, 1421D Google Scholar
Dyson, J. E., Hartquist, T. W., Redman, M. P., et al., 2000, Ap&SS, 272, 197D Google Scholar
Fang, X., et al., 2018, ApJ, 859, 92 CrossRefGoogle Scholar
García-Rojas, J. et al., 2022, MNRAS, 510, 5444G CrossRefGoogle Scholar
Garcia-Segura et al. 2006, ApJ, 646L, 61G Google Scholar
Gonçalves, D. R., Corradi, R. L. M., Mampaso, A., 2001, ApJ, 547, 302G CrossRefGoogle Scholar
Gonçalves, D. R. et al., 2009, MNRAS, 398, 2166G CrossRefGoogle Scholar
Graham, J. R., et al., 1993, ApJ, 408L, 105G CrossRefGoogle Scholar
Kwitter, K. B., Henry, R. B. C., 2022, PASP, 134, 2001 CrossRefGoogle Scholar
López, J. A., V ázquez, R., Rodríguez, L. F., 1995, ApJ, 455, L63 Google Scholar
Manchado, A., et al., 2015, ApJ, 808, 115M CrossRefGoogle Scholar
Mari, M. B., Gonçalves, D. R., Akras, S., 2023a, MNRAS, 518, 3908M CrossRefGoogle Scholar
Mari, M. B., Akras, S., Gonçalves, D. R., 2023b, MNRAS, 525, 1998M CrossRefGoogle Scholar
Marquez-Lugo, R. A., Guerrero, M. A., Ramos-Larios, G., et al., 2015, MNRAS, 453, 1888M CrossRefGoogle Scholar
Matsuura, M., et al., 2009, ApJ, 700, 1067M CrossRefGoogle Scholar
Mellema, G., et al., 1998, A&A, 331, 335M Google Scholar
Monreal-Ibero, A., Walsh, J. R., 2020, A&A. 634A, 47M Google Scholar
Perea-Calderón, J. V., García-Hernández, D. A., García-Lario, P., et al., 2009, A&A, 495L, 5P Google Scholar
Perinotto, M., 2000, Ap&SS, 274, 205 Google Scholar
Ramstedt, S., et al., 2020,A&A, 640A, 133R Google Scholar
Reay et at. 1988, MNRAS, 232, 615R CrossRefGoogle Scholar
Redman, M. P., Viti, S., Cau, P., Williams, D. A., 2003, MNRAS, 345, 1291R CrossRefGoogle Scholar
Speck, K. A., et al., 2002, AJ, 123, 346S CrossRefGoogle Scholar
Steffen, W., López, J. A. 2004, ApJ, 612, 319S CrossRefGoogle Scholar
Sternberg, A., Dalgarno, A., 1989, ApJ, 338, 197S CrossRefGoogle Scholar
Walsh, J. R, et al., 2018, A&A, 620A, 169W Google Scholar
Weigelt, G., et al. 2002, A&A, 392, 131W Google Scholar
Wesson, R., Matsuura, M., Zijlstra, A. A., et al., 2023, arXiv230809027WGoogle Scholar
Woitke, P., 2006, A&A, 452, 537W Google Scholar
Ziurys, L. M., 2006, PNAS, 10312274ZGoogle Scholar