Infrared nebulae around young stellar objects

We present a K-band atlas of 106 reflection nebulae, 41 of which are new discoveries. We observed these nebulae with the University of Hawaii 2.2 m telescope in the course of an imaging survey of 197 objects that were selected as nearby young Class I sources. K-band images and flux-calibrated surface brightness contour plots of each nebula are presented. We found that the near-IR luminosities and physical sizes of the nebulae increase with the bolometric luminosity of the illuminating sources. Only 22 nebulae, about 10% of these candidate Class I sources, have indications of shocked H-2 emission. The great variety of nebulae that we observed prevented us from classifying them based on morphology. However, we note that as the spectral index decreases, the central star is more frequently visible at K band, and the flux from the central star tends to be dominant over the flux from the nebula. For objects that have a higher spectral index, most of the K-band flux is from the reflection nebula, and the central star is less frequently visible. The nebula around IRAS 05450+0019 has a unique morphology, and we speculate that it may be an example of a disk shadow being projected into the surrounding cloud. We present J-, H-, and K-band images of this object with surface brightness contours, as well as its spectral energy distribution from 1.2 to 100 mu m.