Hubble Space Telescope NICMOS imaging of disks and envelopes around very young stars

We present HST/NICMOS observations with similar to 0."1 approximate to 15 A U resolution of six young stellar objects in the Taurus star formation regi on. The targets of our survey are three Class I IRAS sources (IRAS 04016 2610, IRAS 04248 + 2612, and IRAS 04302 + 2247) and three low-luminosity st ars (DG Tau B, Hare 6-5B, and CoKu Tau/1) associated with Herbig-Haro jets. The broadband images show that the near-infrared radiation from these sour ces is dominated by light scattered from dusty circumstellar material distr ibuted in a region 10-15 times the size of our solar system. Although the d etailed morphologies of the individual, objects are unique, the observed yo ung stellar objects share common features. All of the circumstellar reflect ion nebulae are crossed by dark lanes from 500 to 900 AU in extent and from less than 50 to 350 AU in apparent thickness. The absorption lanes extend perpendicular to known optical and millimeter outflows in these sources. We interpret the dark lanes as optically thick circumstellar disks seen in si lhouette against bright reflection nebulosity. The bipolar reflection nebul ae extending perpendicular to the dust lanes appear to be produced by scatt ering from the upper and lower surfaces of the disks and from dusty materia l within or on the walls of the outflow cavities. Of five objects in which the central source is directly detected, two are found to be subarcsecond b inaries. This minisurvey is the highest resolution near-infrared study to d ate of circumstellar environments around solar-type stars with age less tha n or equal to 1 Myr.