| Northern Monoceros is a region rich in emission nebulosity, opaque clouds, dark globules, and young open clusters and could be considered a good environment and laboratory to detect and study young stellar objects. From this region we have studied the young open clusters NGC 2244(C0629+049) and NGC 2264(C0638+099), known to be sites of very active star formation and which are among the youngest in the Galaxy ({dollar}tsb{lcub}age{rcub} approx{dollar} 4-6 {dollar}times{dollar} {dollar}10sp6{dollar} yr).; We have secured stellar data in the cluster fields with different photometric systems (Stromgren, Walraven, Johnson, Cousins, and near-infrared) and the spectroscopic system, IDS, in three observing seasons (1985, 86, and 87). These new data allowed us to assess membership, spectral types and to estimate extinctions, distances, abundances, variability, cluster ages and masses, and several other important astrophysical parameters.; The picture that emerges from the analysis is that the cluster NGC 2244 seems to be formed only by massive stars (OB-type), whereas, two well differentiated groups of massive stars (some Herbig Ae/Be and main sequence stars with moderate or small infrared excesses) and low-mass stars (emission lines and T Tauri stars) appear to form NGC 2264. It was also found that the clusters lie in different arms of the Galaxy and they have been originated by dissimilar mechanisms in different epochs. |
