Abundances of PNe in the Outer Disk of M31

TL;DR

This study presents spectroscopic data and chemical abundance analysis of 16 planetary nebulae in M31's outer disk, revealing similarities to Milky Way PNe and a shallower oxygen abundance gradient.

Contribution

It provides the first direct temperature-based abundance measurements for PNe in M31's outer disk and compares their properties to Galactic counterparts.

Findings

PNe in M31's outer disk show similar abundance correlations to Milky Way PNe.

The oxygen abundance gradient in M31's outer disk is shallower than in the Milky Way.

Sample PNe likely originated from stars near 2 solar masses.

Abstract

We present spectroscopic observations and chemical abundances of 16 planetary nebulae (PNe) in the outer disk of M31. The [O III] 4363 line is detected in all objects, allowing a direct measurement of the nebular temperature essential for accurate abundance determinations. Our results show that the abundances in these M31 PNe display the same correlations and general behaviors as Type II PNe in the Milky Way Galaxy. We also calculate photoionization models to derive estimates of central star properties. From these we infer that our sample PNe, all near the peak of the Planetary Nebula Luminosity Function, originated from stars near 2 M_sun. Finally, under the assumption that these PNe are located in M31's disk, we plot the oxygen abundance gradient, which appears shallower than the gradient in the Milky Way.