A Highly Collimated, Young, and Fast CO Outflow in OMC-1 South

Abstract

We present high angular resolution (∼ 1 ′′ ), sensitive CO(2-1) line observations of the region OMC1 South in the Orion Nebula made using the Submillimeter Array (SMA). We detect the CO(2-1) high velocity outflow that was first found by Rodríguez-Franco et al. (1999a) with the IRAM 30 m. Our observations resolve the outflow, whose velocity-integrated emission has a deconvolved width of 0. "89 ± 0. "06 (390 AU) and a projected length of ∼ 48 ′′ (21,000 AU) with very high redshifted and blueshifted gas with velocities of about ±80 km s −1 . This outflow is among the most collimated (∼ 3 • ) and youngest outflows (600 yr) that have been reported. The data show that this collimated outflow has been blowing in the same direction during the last 600 yr. At high velocities, the CO(2-1) outflow traces an extremely collimated jet, while at lower velocities the CO emission traces an envelope possibly produced by entrainment of ambient gas. Furthermore, we also detect for the first time a millimeter wavelength continuum source possibly associated with a class I protostar that we suggest could be the possible exciting source for this collimated outflow. However, the bolometric luminosity of this source appears to be far too low to account for the powerful molecular outflow.Subject headings: stars: pre-main sequence -ISM: jets and outflows -ISM: individual: (Orion-S, OMC1-S, M42) -

Silicon Monoxide Observations Reveal a Cluster of Hidden Compact Outflows in the OMC 1 South Region

“…Even when the situation in this case is not as critical as in the CO outflow reported by Zapata et al (2005), in which the kinematic luminosity of the outflow seems to exceed the bolometric luminosity of the exciting source, it is still very difficult to explain the large kinematic luminosity of this SiO outflow. Statistically, the kinematic luminosity of outflows is only of order 0.001Y0.01 of the bolometric luminosity of the exciting source ( Wu et al 2004).…”

“…The scale bar indicates the 1.3 mm continuum emission in mJy beam À1 . This image was taken from Zapata et al (2005). Bottom: SMA SiO J ¼ 5 !…”

“…The top panel shows the 12 CO J ¼ 2 ! 1 highly collimated ($3 ) and fast ($AE80 km s À1 ) bipolar outflow and the 1.3 mm continuum emission imaged by Zapata et al (2005). The exciting source of this outflow seems to be the source 136-359 or the infrared source [GWV98] C (Gaume et al 1998).…”

“…The half-power contour of the synthesized beam is shown in the bottom left corner of the image. The purple stars indicate the position of the presumed exciting sources of the SiO molecular outflows (137-347, B, C, and 137-408, see Gaume et al 1998;Zapata et al 2004bZapata et al , 2005. The purple asterisk marks the position of the infrared source TPSC-1 ( Lada et al 2000).…”

“…This region indeed seems to be the youngest and most active zone of star formation in the nebula, showing extremely well collimated molecular outflows and at least a half-dozen extended and powerful Herbig-Haro ( HH ) flows emanating from it (Schmid-Burgk et al 1990;Bally et al 2000;Rosado et al 2001;O'Dell & Doi 2003;Zapata et al 2005).…”