AAS 195th Meeting, January 2000
Session 78. Young Stars, Disks and Planets
Display, Friday, January 14, 2000, 9:20am-6:30pm, Grand Hall

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[78.09] Shocks and Precursors in the Cepheus A Outflow as Observed by HST

P. Hartigan (Rice Univ.), J. Morse (CASA), J. Bally (CASA)

We present new H\alpha, [S~II], and [O~III] HST images of the Cepheus A outflow near GGD 37. The optical emission appears as a frothy bubble that consistently lies ~ 1 arcsecond within the edges of the flow defined by high spatial resolution ground-based H2 images. A close examination of the HST data shows that [S~II] emits faintly ahead of the shocks defined by the H\alpha emission, in the same locations where H2 is strong. The H2 and [S~II] emission appear to be part of a precursor that accelerates and heats molecular and atomic gas laterally to the main flow, providing the first clear view as to how stellar jets accelerate molecular flows.

Additional discoveries include a bow shock that appears to be breaking up into smaller bows, each with strong [O~III] emission; new T Tauri stars that drive jets unrelated to the main outflow; the first clear images of the high proper motion source HW; and resolution of the complex cooling zone along the edge of the outflow. New long-slit velocity maps of the H2 emission provide additional insight into the transfer of momentum and energy from the jet to the molecular flow.

Support for this work was provided by NASA through grant number GO-6562 from STScI, operated by AURA Inc., under NASA contract NAS5-26555.

The author(s) of this abstract have provided an email address for comments about the abstract: hartigan@sparky.rice.edu

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