Energetic feedback and ${}^{26}$Al from massive stars and their supernovae in the Carina region

Abstract

We study the populations of massive stars in the Carina region and their energetic feedback and ejection of ${}^{26}$Al. We did a census of the stellar populations in young stellar clusters within a few degrees of the Carina Nebula. For each star we estimated the mass, based on the spectral type and the host cluster age. We used population synthesis to calculate the energetic feedback and ejection of ${}^{26}$Al from the winds of the massive stars and their supernova explosions. We used 7 years of INTEGRAL observations to measure the ${}^{26}$Al signal from the region. The INTEGRAL ${}^{26}$Al signal is not significant with a best-fit value of about 1.5e-5 ph/cm^2/s, approximately half of the published Compton Gamma Ray Observatory (CGRO) result, but in agreement with the latest CGRO estimates. Our analysis of the stellar populations in the young clusters leads to an expected signal of half the observed value, but the results are consistent within 2 sigma. We find that the fraction of ${}^{26}$Al ejected in Wolf-Rayet winds is high, and the observed signal is unlikely to be caused by ${}^{26}$Al ejected in supernovae alone, indicating a strong wind ejection of ${}^{26}$Al. Due to the lack of prominent O stars, regions with ages $\gtrsim$10 Myr are often neglected in studies of OB associations. We find that in the Carina region such clusters contribute significantly to the stellar mass and the energetics of the region.

Accepted for publication in A&A