Spitzer 24 um Images of Planetary Nebulae

TL;DR

This study uses Spitzer 24 um images to analyze the emission characteristics of 36 Galactic planetary nebulae with hot central stars, revealing an evolutionary sequence based on their infrared and H-alpha emission properties.

Contribution

First comprehensive analysis of 24 um emission in planetary nebulae with hot central stars, linking infrared features to nebular evolution and composition.

Findings

Diffuse 24 um emission detected in 28 PNe

Three types of emission morphology identified

Evolutionary sequence suggested based on emission properties

Abstract

Spitzer MIPS 24 um images were obtained for 36 Galactic planetary nebulae (PNe) whose central stars are hot white dwarfs (WDs) or pre-WDs with effective temperatures of ~100,000 K or higher. Diffuse 24 um emission is detected in 28 of these PNe. The eight non-detections are angularly large PNe with very low H-alpha surface brightnesses. We find three types of correspondence between the 24 um emission and H-alpha line emission of these PNe: six show 24 um emission more extended than H-alpha emission, nine have a similar extent at 24 um and H-alpha, and 13 show diffuse 24 um emission near the center of the H-alpha shell. The sizes and surface brightnesses of these three groups of PNe and the non-detections suggest an evolutionary sequence, with the youngest ones being brightest and the most evolved ones undetected. The 24 um band emission from these PNe is attributed to [O IV] 25.9 um and [Ne V] 24.3 um line emission and dust continuum emission, but the relative contributions of these three components depend on the temperature of the central star and the distribution of gas and dust in the nebula.