Characterizing the Youngest Herschel-detected Protostars. II. Molecular Outflows from the Millimeter and the Far-infrared

Abstract

We present Combined Array for Research in Millimeter-wave Astronomy (CARMA) CO (J=1\to 0) observations and Herschel PACS spectroscopy, characterizing the outflow properties toward extremely young and deeply embedded protostars in the Orion molecular clouds. The sample comprises a subset of the Orion protostars known as the PACS Bright Red Sources (PBRS; Stutz et al.). We observed 14 PBRS with CARMA and 8 of these 14 with Herschel, acquiring full spectral scans from 55 to 200 μm. Outflows are detected in CO (J=1\to 0) from 8 of 14 PBRS, with two additional tentative detections; outflows are also detected from the outbursting protostar HOPS 223 (V2775 Ori) and the Class I protostar HOPS 68. The outflows have a range of morphologies; some are spatially compact, <10,000 au in extent, while others extend beyond the primary beam. The outflow velocities and morphologies are consistent with being dominated by intermediate inclination angles (80° ≥ I ≥ 20°). This confirms the interpretation of the very red 24-70 μm colors of the PBRS as a signpost of high envelope densities, with only one (possibly two) cases of the red colors resulting from edge-on inclinations. We detect high-J (J _up > 13) CO lines and/or H₂O lines from 5 of 8 PBRS and only for those with detected CO outflows. The far-infrared CO rotation temperatures of the detected PBRS are marginally colder (∼230 K) than those observed for most protostars (∼300 K), and only one of these five PBRS has detected [O I] 63 μm emission. The high envelope densities could be obscuring some [O I] emission and cause a ∼20 K reduction to the CO rotation temperatures.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.