Molecular Outflows from X-Ray–Emitting Protostars in the ρ Ophiuchi Dark Cloud

Abstract

We report CO (J = 2-1, J = 1-0) outflows from four X-ray-emitting protostars (EL29, IRS44, WL6, WL10) in the ρ Ophiuchi cloud core which have been firmly identified with the X-ray satellite ASCA. The common feature of these outflows is that the blue and red lobes are largely overlapped, which indicates that the inclination angle between the outflow axis and line of sight is smaller than 30° (nearly pole-on configuration). Taking account of the hard X-ray transparency (NH ~ 1023 cm-2) and the column density of a circumstellar disk (NH > 1024 cm-2), it is naturally understood that hard X-rays emitted near the surface of protostars or the inner part of the disk are observed in the nearly pole-on configuration. The outflow detection rate (4/5) in the present observations shows that a low-mass protostar emits X-rays even in the outflow phase of early stellar evolution.