Opening PANDORA's box: APEX observations of CO in PNe

TL;DR

This study used APEX telescope observations of CO (J=3-2) emission to analyze the molecular gas in 93 proto-planetary and planetary nebulae, revealing detection rates and estimating physical parameters of the circumstellar shells.

Contribution

First large survey of CO (J=3-2) in a significant sample of proto-planetary and planetary nebulae, providing new data on molecular gas properties and detection rates.

Findings

CO (J=3-2) detected in 21 of 93 objects

Detection rate of 100% in proto-planetary nebulae

Estimated column densities and masses of molecular gas

Abstract

Context. Observations of molecular gas have played a key role in developing the current understanding of the late stages of stellar evolution. Aims. The survey Planetary nebulae AND their cO Reservoir with APEX (PANDORA) was designed to study the circumstellar shells of evolved stars with the aim to estimate their physical parameters. Methods. Millimetre carbon monoxide (CO) emission is the most useful probe of the warm molecular component ejected by low- to intermediate-mass stars. CO is the second-most abundant molecule in the Universe, and the millimeter transitions are easily excited, thus making it particularly useful to study the mass, structure, and kinematics of the molecular gas. We present a large survey of the CO (J = 3 - 2) line using the Atacama Pathfinder EXperiment (APEX) telescope in a sample of 93 proto-planetary nebulae and planetary nebulae. Results. CO (J = 3 - 2) was detected in 21 of the 93 objects. Conclusions. CO (J = 3 - 2) was detected in all 4 observed pPNe (100%), 15 of the 75 PNe (20%), one of the 4 wide binaries (25%), and in 1 of the 10 close binaries (10%). Using the CO (J = 3 - 2) line, we estimated the column density and mass of each source.