Tracing the ejecta from cosmic nucleosynthesis

Abstract: Long-lived radioactive by-products of nucleosynthesis provide an opportunity to trace the flow of ejecta away from its sources for times beyond where ejecta can be seen otherwise. Gamma rays from such radioactive decay in interstellar space can be measured with space-borne telescopes. A prominent useful example is 26Al with a radioactive decay time of one My. Such observations have revealed that typical surroundings of massive stars are composed of large cavities, extending to kpc sizes. Implications are that material recycling into new stars is twofold: rather direct as parental clouds are hosts to new star formation triggered by feedback, and more indirect as these large cavities merge with ambient interstellar gas after some delay. Kinematic measurements of hot interstellar gas carrying such ejecta promises important measurements complementing stellar and dense gas kinematics.