Discovery of a young massive stellar cluster associated with IRAS source 16177-5018

We report the discovery of a young massive stellar cluster embedded in an extended H II region, invisible at optical wavelengths where the extinction is A(V) approximate to 28 mag, associated with the IRAS source 16177-5018. J-, H-, and narrowband K-imaging photometry combined with the K-s Two Micron All Sky Survey data show the presence of sources with excess infrared emission at 2.2 mum, concentrated in an area of about 1 pc(2) around a massive young stellar object identified as the IRAS source. This object has a near mid-infrared spectral index between 2.2 and 25 mum alpha(IR) = d log(lambdaF(lambda))/d log lambda = 4.78, characteristic of compact H II regions, with bolometric luminosity inferred from the integrated near-to-far-infrared flux density of 2.8 x 10(5) L., which corresponds to a zero-age main-sequence star of about 42 M.. From the color-magnitude diagram we were able to classify the majority of the cluster members as reddened massive stars earlier than spectral type B5.