Submillimeter Array Observations of L1551 IRS 5 in CS (J=7-6)

Abstract

We have imaged the circumstellar envelope around the binary protostar L1551 IRS 5 in CS (J=7-6) and 343 GHz continuum emission at ~ 3 arcsec resolution using the Submillimeter Array. The continuum emission shows an elongated structure (~ 220 x 100 AU) around the binary perpendicular to the axis of the associated radio jet. The CS emission extends over ~ 400 AU, appears approximately circularly symmetric, and shows a velocity gradient from southeast (blueshifted) to northwest (redshifted). The direction of the velocity gradient is different from that observed in C18O (J=1-0). This may be because rotation is more dominant in the CS envelope than the C18O envelope, in which both infall and rotation exist. The CS emission may be divided into two velocity components: (1) a "high" velocity disk-like structure surrounding the protostar, +-1.0 - 1.5 km s-1 from the systemic velocity, and (2) a "low" velocity structure, located southwest of the protostar, < 1.0 km s -1 from the systemic velocity. The high-velocity component traces warm and dense gas with kinematics consistent with rotation around the protostar. The low-velocity component may arise from dense gas entrained in the outflow. Alternatively, this component may trace infalling and rotating gas in an envelope with a vertical structure.

14 pages, 4 figures

References in corpus (5)

• The Submillimeter Array
• Tracing the envelopes around embedded low-mass young stellar objects with HCO+ and millimeter-continuum observations
• From infall to rotation around young stellar objects: A transitional phase with a 2000 AU radius contracting disk?
• A Comprehensive Study of the L1551 IRS 5 Binary System
• Formation of an Infalling Disklike Envelope around a Protostar

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