The stellar population associated with IRAS source 16132-5039

Abstract

We report the discovery of a young massive stellar cluster and infrared nebula in the direction of the CS molecular cloud associated to the IRAS point source 16132-5039. The analysis of the mid-infrared images from the more accurate MSX catalog, reveled that there are two independent components associated with the IRAS source. The integral of the spectral energy distribution for these components, between 8.28 $μ$m and 100 $μ$m, gave lower limits for the bolometric luminosity of the embedded objects of $8.7 \times 10^4 L_\odot$ and $9 \times 10^3 L_\odot$, which corresponds to ZAMS O8 and B0.5 stars, respectively. The number of Lyman continuum photons expected from the stars that lie along the reddening line for early-type stars is about 1.7 $ \times$ 10$^{49}$ s$^{-1}$, enough to produce the detected flux densities at 5 GHz. The NIR spectrum of the nebula increases with frequency, implying that free-free emission cannot be the main source of the extended luminosity, from which we conclude that the observed emission must be mainly dust scattered light. A comparison of the cluster described in this paper with the young stellar cluster associated with the IRAS source 16177-5018, which is located at the same distance and direction, shows that the mean visual absorption of the newly discovered cluster is about 10 magnitudes smaller and it contains less massive stars, suggesting that it was formed from a less massive molecular cloud.