The population of Galactic planetary nebulae: a study of distance scales and central stars based on the second GAIA release

TL;DR

This study uses Gaia DR2 parallaxes to calibrate distances to Galactic planetary nebulae, improving existing scales and analyzing the properties of their central stars in relation to stellar evolution.

Contribution

It provides a new, more accurate distance scale for Galactic PNe based on Gaia parallaxes and compares these with previous measurements, also analyzing central star properties.

Findings

Good correlation between Gaia and literature parallaxes.

Derived an improved distance scale for PNe.

Placed central stars on the HR diagram consistent with post-AGB evolution.

Abstract

We matched the astrometry of central stars (CSs) of spectroscopically-confirmed Galactic planetary nebulae (PNe) with DR2 Gaia parallaxes ($p$), finding 430 targets in common with $p>0$ and $|\sigma_{\rm p}/p|<1$. A catalog of PNe whose CSs have DR2 Gaia parallaxes is presented in Table 1. We compared DR2 parallaxes with those in the literature, finding a good correlation between the two samples. We used PNe parallaxes to calibrate the Galactic PN distance scale. Restricting the sample to objects with 20$\%$ parallax accuracy, we derive the distance scale ${\rm log}(R_{\rm pc})=-(0.226\pm0.0155)\times{\rm log}(S_{\rm H\beta})-(3.920\pm0.215)$, which represents a notable improvement with respect to previous ones. We found that the ionized mass vs. optical thickness distance scale for Galactic PNe is not as well constrained by the Gaia calibrators, but gives important insight on the nature of the PNe, and is essential to define the domain for our distance scale application. We placed the CSs whose distance has been determined directly by parallax on the HR diagram, and found that their location on the post-AGB H-burning evolutionary tracks is typical for post-AGB stars.