High-resolution Very Large Array observations of 18 MIPSGAL bubbles

TL;DR

This study uses high-resolution radio observations of 18 MIPSGAL bubbles to classify their morphology, identify stellar types, and estimate their distances, revealing insights into the nature of evolved stars and planetary nebulae in our galaxy.

Contribution

It provides the first detailed radio morphological classification of MIPSGAL bubbles and links specific features to stellar types, enhancing understanding of their evolutionary stages.

Findings

Three bubbles are associated with luminous blue variable star candidates.

Eleven bubbles are likely planetary nebulae based on their elliptical shape and lack of central radio source.

The MIPSGAL bubbles catalog may contain a large fraction of Galactic planetary nebulae within 1.4 to 6.9 kpc.

Abstract

We present radio observations of 18 MIPSGAL bubbles performed at 5 GHz (6 cm) with the Karl G. Jansky Very Large Array in configuration B and BnA. The observations were aimed at understanding what kind of information high-resolution and high-sensitivity radio maps can supply on the circumstellar envelopes of different kinds of evolved stars and what their comparison with infrared images with similar resolution can tell us. We found that the 18 bubbles can be grouped into five categories according to their radio morphology. The three bubbles presenting a central point source in the radio images all correspond to luminous blue variable star candidates. Eleven bubbles show an elliptical shape and the total lack of a central object in the radio, and are likely associated with planetary nebulae. Under this assumption we derive their distance, their ionized mass and their distribution on the Galactic plane. We discuss the possibility that the MIPSGAL bubbles catalogue (428 objects) may contain a large fraction of all Galactic planetary nebulae located at a distance between 1.4 kpc and 6.9 kpc and lying in the MIPSGAL field of view. Among the remaining bubbles we identify also a H II region and a proto-planetary nebula candidate.