| In this thesis I investigate the Milky Way's optically obscured population of evolved massive stars and massive star-forming regions using near-infrared photometry and spectroscopy. We have developed a near-infrared survey technique with narrow band filters aimed at detecting the vast majority of evolved massive stars whose abode is the dusty Galactic disk, and we have successfully applied this technique to discover four new Wolf-Rayet stars. In addition to evolved massive stars, we discovered young hot stars and sites of star formation with our survey data, and our observations and analysis of these regions are also presented.; For historical reasons, much of the classification and analysis of hot stars has been in the optical. Therefore, we obtain near-infrared spectra for a sample of Galactic Wolf-Rayet stars to use as templates for those found in current and future surveys, and demonstrate that stellar parameters can be determined from near-infrared spectra. We find higher stellar temperatures than in previous analyses due to the inclusion of line-blanketing in the comparison models, and lower mass loss rates due to the consideration of clumping. The lower mass loss rates derived here alleviate the WR “momentum problem” for most stars in our sample.; A near-infrared broad band survey of the Galaxy's most massive embedded star-forming region, W49A, reveals a previously unknown massive stellar cluster. Over 100 stars with inferred masses M > 20 are detected, placing W49A at the high-mass end of the continuum of young Milky Way star clusters. These results emphasize the importance of combining near-infrared observations with those at radio, far-, and mid-infrared wavelengths for a complete picture of star formation events. |
