Discovery of a Young Massive Stellar Cluster Associated withIRASSource 16177-5018

We report the discovery of a young massive stellar cluster embedded in anextended HII region, invisible at optical wavelengths where the extinction is$A_V \approx 28$ magnitudes, associated with the IRAS source 16177-5018. $J, H$and nb$K$ imaging photometry combined with the $K_S$ 2MASS data show thepresence of sources with infrared excess emission at 2.2 $\mu$m, concentratedin an area of about one square parsec around a massive young stellar objectidentified as the IRAS source. This object has a near-mid infrared spectralindex betweem 2.2 and 25 $\mu$m $\alpha({\rm IR}) = d {\rm log}(\lambdaF_\lambda)/d {\rm log} \lambda $ =4.78, characteristic of compact H II regions,with bolometric luminosity, inferred from the integrated near to far-infraredflux density of $2.8 \times 10^5 L_\odot$, which corresponds to a ZAMS star ofabout $42 M_\odot$. From the color-magnitude diagram we were able to classifythe majority of the cluster members as reddened massive stars earlier thanspectral type B5.Comment: 11 page, 10 figures (figure3 in jpeg format), Astronomical Journal - Accepte