Dissection of the protostellar envelope surrounding IRAS 05173 − 0555 in L 1634

Context. The youngest protostars that power energetic outflows are surrounded by infalling and rotating envelopes that contain most of the mass of the system. Aims. To study the properties and kinematics of the protostellar envelope surrounding the embedded source IRAS 05173−0555 in L1634. Methods. We carried out VLA ammonia observations at 1.3 cm with the VLA in the D configuration to map the gas towards the core of L1634. Results. The NH 3 emission towards IRAS 05173−0555 is resolved and shows two components clearly distinguishable morphologically: a cross-like structure, roughly elongated in the direction of the HH 240/241 outflow and associated with IRAS 05173−0555, plus an arc-like stream elongated towards the north. The properties and kinematics of the gas suggest that the origin of the cross-like morphology could be the interaction between the outflow and the envelope. A more compact and flattened structure, which could be undergoing rotation about the axis of the outflow, has been detected towards the center of the cross-like envelope. The northern stream, which has properties and velocity different from those of the cross-like envelope, is likely part of the original cloud envelope, and could be either a quiescent core that would never form stars, or be in a prestellar phase.