THE INFRARED MORPHOLOGY OF YOUNG STELLAR OBJECTS WITHOUT COMPANIONS - A SPECKLE INTERFEROMETRIC STUDY

One-dimensional speckle interferometric techniques are employed in the near-infrared wavelength range of 1.25 to 4.8 mum to ascertain the morphology of eighteen young stellar objects not known to have associated companions. We find that three of these objects are resolved as core/halo distributions or are partially resolved with a high level of confidence. Five other sources probably show some structure although the confidence level is lower. The ten remaining sources either show evidence for very small angular scale structure or are unresolved with an upper limit of about 0.2 arcsec. Our results are compared to other published angular size data. A relationship between the 12 to 25 mum spectral slope and the physical extent of the material in the near infrared is discovered and compared to simple models. We interpret this relationship as an indication that the effective scale size of circumstellar matter surrounding young stellar objects decreases with advancing age.