Unveiling the Circumstellar Envelope and Disk: A Sub-Arcsecond Survey of Circumstellar Structures

We present the results of a λ = 2.7 mm continuum interferometric survey of 24 young stellar objects in 11 fields. The target objects range from deeply embedded Class 0 sources to optical T Tauri sources. This is the first sub-arcsecond survey of the λ = 2.7 mm dust continuum emission from young, embedded stellar systems. These multi-array observations, utilizing the high dynamic u,v range of the BIMA array, fully sample spatial scales ranging from 0. 4 to 60, allowing the first consistent comparison of dust emission structures in a variety of systems. The images show a diversity of structure and complexity. The optically visible T Tauri stars (DG Tauri, HL Tauri, GG Tauri, and GM Aurigae) have continuum emission dominated by compact (≤ 1) circumstellar disks. In the cases of HL Tauri and DG Tauri, the disks are resolved. The more embedded near-infrared sources (SVS13 and L1551 IRS5) have continuum emission that is extended and compact. The embedded sources (L1448 IRS3, NGC1333 IRAS2, NGC1333 IRAS4, VLA 1623, and IRAS 16293-2422) have continuum emission dominated by the extended envelope, typically ≥ 85% of the emission at λ = 2.7 mm. In fact, in many of the deeply embedded systems it is difficult to uniquely isolate the disk emission component from the envelope extending inward to AU size scales. Simple estimates of the circumstellar mass in the optical/infrared and embedded systems range from 0.01-0.08 M⊙and 0.04-2.88 M⊙, respectively. All of the target embedded objects are in multiple systems with separations on scales of ∼ 30 or less. Based on the system separation, we place the objects into three categories: separate envelope (separation ≥ 6500 AU), common envelope (separation 150-3000 AU), and common disk (separation ≤ 100 AU). These three groups can be linked with fragmentation events during the star formation process: separate envelopes from prompt initial fragmentation and the separate collapse of a loosely condensed Current Address: Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany Email: [email protected]