On the origin of optical and IR emission lines in star-forming galaxies

ABSTRACT Combining the cloudy photoionization code with updated stellar population synthesis results, we simultaneously model the MIR $\rm{[Ne {}{\small III}]}/\rm{[Ne {}{\small II}]}$ versus $\rm{[O {}{\small IV}]}/\rm{[Ne {}{\small III}]}$, the MIR-FIR $\rm{[Ne {}{\small III}]}/\rm{[Ne {}{\small I...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Veröffentlicht in:Monthly notices of the Royal Astronomical Society 2023-08, Vol.525 (2), p.2916-2934
Hauptverfasser: Martínez-Paredes, Mariela, Bruzual, Gustavo, Morisset, Christophe, Kim, Minsun, Meléndez, Marcio, Binette, Luc
Format: Artikel
Sprache:eng
Online-Zugang:Volltext bestellen
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Beschreibung
Zusammenfassung:ABSTRACT Combining the cloudy photoionization code with updated stellar population synthesis results, we simultaneously model the MIR $\rm{[Ne {}{\small III}]}/\rm{[Ne {}{\small II}]}$ versus $\rm{[O {}{\small IV}]}/\rm{[Ne {}{\small III}]}$, the MIR-FIR $\rm{[Ne {}{\small III}]}/\rm{[Ne {}{\small II}]}$ versus $\rm{[O {}{\small IV}]}/\rm{[O {}{\small III}]}$ and the classical BPT diagnostic diagrams. We focus on the properties of optically classified H ii galaxies that lie in the normal star forming zone in the MIR diagnostic diagram. We find that a small fraction of our models lie in this zone, but most of them correspond to the lowest explored metallicity, Z*  =  0.0002, at age ∼1 Gyr. This value of Z* is, by far, lower than the values derived for these galaxies from optical emission lines, suggesting that the far-UV emission produced by post-AGB stars (a.k.a. HOLMES, hot low-mass evolved stars) is NOT the source of ionization. Instead, shock models can easily reproduce this part of the MIR diagram. We suggest that it is likely that some of these galaxies have been misclassified and that in them, shocks, produced by a weak AGN-outflow, could be an important source of ionization. Using a subset of our models, we derive a new demarcation line for the maximal contribution of retired galaxies in the BPT diagram. This demarcation line allows for a larger contamination from the neighbouring AGN-dominated region. Considering the importance of disentangling the different ionizing mechanisms in weak or deeply obscured systems, new observational efforts to classify galaxies both in the optical and IR are required to better constrain this kind of models and understand their evolutionary paths.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stad2447