The circumstellar medium around evolved massive stars

Abstract

The interplay between evolved massive stars (e.g., Of, B[e], red supergiant, luminous blue variable) and their surroundings is one of the less known issues in galactic astrophysics. In this article we report the first results of an observational campaign aiming to shed light on the evolution of the molecular gas as a consequence of massive star evolution. These results are presented in the form of maps (4′ × 4′ of maximum size), corresponding to the mm- and submm-wavclcngths transitions of CO and 13CO. Most of the observations were performed using the 10 m SMT radiotelescope at Arizona. We have detected tens of M⊙ of molecular gas, surrounding already known optical/IR nebula of ionized gas and warm dust. This molecular gas seems to be compressed in some parts, up to densitics of several 104 cm-3, probably by the action of strong and variable stellar winds and mass ejections. The CO opacity is also variable within a given field. These promising first results encourage both the study of new regions and the search for more complex molecular species in selected parts of these particular scenarios.