Description
Background: Planetary nebulae (PNe) are common in both young and old stellar populations. The planetary nebula luminosity function (PNLF) is used as a cosmological distance indicator out to the Coma cluster. The PNLF is reproduced in models only by assuming substantial internal dust extinction for PNe, but observational studies of Galactic PNe have been unable to corroborate extinction beyond foreground. PNe extinction measurements are challenging, but accurate determinations are required to unpick interstellar and intranebular PNe extinction.
Method: We use central star (CSPN) identifications from Gaia to measure new, accurate PNe extinctions. Extinction fitting using the Fitzpatrick 1999 dust extinction law is added to the PySSED tool, which fits stellar atmosphere models to available photometry. The fitted extinctions are compared to Balmer decrement extinctions of nebular ionized gas and to tomographic foreground extinctions. Thin-shell PNe morphologies mean internal extinction affects ionized gas more than CSPNe.
Results: In a sample of diffuse PNe (angular sizes >1’), our results are in good agreement with the most accurate literature extinction determinations. Many PNe show no evidence of internal extinction. However, some of the most compact PNe within our sample (e.g. NGC 6781) display evidence of internal extinction through comparisons with both interstellar dust maps and nebular Balmer decrements.
Conclusion: Our central star extinctions help resolve inconsistencies regarding existing measured PNe extinctions. Our results demonstrate the presence of internal extinction in some compact PNe, which is absent when considering more evolved / diffuse PNe. This finding is consistent with dust extinction influencing the PNLF.
