AAS 199th meeting, Washington, DC, January 2002
Session 134. Formation of Massive Stars
Display, Thursday, January 10, 2002, 9:20am-4:00pm, Exhibit Hall

[134.11] W75N: Molecular Outflows & IR Emission from a cluster of early B stars

D.P. Stark (University of Wisconsin), D.S. Shepherd (National Radio Astronomy Observatory), L. Testi (Arcetri Observatory)

We present 2'' to 7'' resolution OVRO 3mm continuum and CO(J=1-0) line emission toward the massive star formation region W75 N. We compare the millimeter emission with infrared images obtained in the K-band continuum and shocked molecular hydrogen line. CO mosaic observations covering a 5' x 2' region centered on a cluster of early B stars show that at least 3 embedded sources contribute to the large scale CO outflow. A mostly NE-SW flow is centered on the ultracompact (UC) HII regions and has a mass of 165 M\odot with a mass outflow rate of 1.2 \times 10-3 M\odot/year and total energy 3.4 \times 1047 ergs. The outflow parameters are consistent with those expected from a B1 star or several B2 stars. At a distance of 2 kpc, this outflow measures 3.7 pc from end-to-end and has a dynamical age of roughly 4 \times 104 years. Two arcsec resolution images of the CO emission indicate that at least two UC HII regions and the millimeter core, MM2, are associated with high-velocity gas which implies that the embedded protostars are in an active outflow phase. The K-band reflection nebula has multiple peaks and extensions which, again, suggests the presence of several outflows.

A more E-W outflow originates from MM2 located approximately 4'' from the UC HII regions. Only the blue-shifted outflow lobe can be identified in the images. A lower limit on the outflow mass is 90 Msun.

Previous observations of 21'' resolution CO and shocked H2 emission indicated that the east-west flow may have been driven by a single, powerful jet. Our line and continuum millimeter images and(deeper)H2 images fail to reveal the presence of a well-collimated jet.

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.