A spider-like outflow in Barnard 5 - IRS 1: The transition from a collimated jet to a wide-angle outflow?

Abstract

We present line and continuum observations made with the Submillimeter Array of the young stellar object Barnard 5 - IRS1 located in the Perseus molecular cloud. Our 12CO(2-1) line observations resolve the high-velocity bipolar north-east-south-west outflow associated with this source. We find that the outflowing gas shows different structures at three different velocity regimes, in both lobes, resulting in a spider-like morphology. In addition to the low-velocity, cone-like (wide-angle) lobes that have previously been observed, we report the presence of intermediate-velocity parabolic shells emerging very close to the Class I protostar, as well as high-velocity molecular bullets that appear to be associated with the optical/IR jet emanating from this source. These compact high-velocity features reach radial velocities of about 50 km s-1 away from the cloud velocity. We interpret that the peculiar spider-like morphology is a result of the molecular material being entrained by a wind with both a collimated jet-like component and a wide-angle component. We suggest that the outflow is in a transitional evolutionary phase between a mostly jet-driven flow and an outflow in which the entrainment is dominated by the wide-angle wind component. We also detect 1300 μm continuum emission at the position of the protostar, which likely arises from the dusty envelope and disc surrounding the protostar. Finally, we report the detection of 13CO(2-1) and SO(65- 54) emission arising from the outflow and the location of the young stellar object. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.