L1157: Interaction of the molecular outflow with the Class 0 environment

¹ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
² Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
³ Institut de Radio Astronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France
⁴ Laboratoire d'Astrophysique de l'Observatoire de Grenoble, BP 53, 38041 Grenoble, France

Corresponding author: F. Gueth, gueth@iram.fr

Received: 28 July 2003
Accepted: 3 December 2003

Abstract

We present high angular resolution interferometric observations of the dust continuum at 2.7 and 1.3 mm, and of the HC₃N () and C¹⁸O () emission around L1157-mm, a Class 0 object that drives a spectacular molecular outflow. The millimeter dust emission is clearly resolved into two components, a flattened compact source of ~ AU at 1.3 mm, and mass ~0.1 , plus an extended envelope of ~3000 AU at 1.3 mm, and mass ~1.1 . The millimeter spectral index varies throughout the region, with the lower value found toward the compact protostar, possibly indicating grain growth in the denser regions. A strong interaction between the molecular outflow and the close protostellar environment is taking place and affects the structure of the innermost parts of the envelope. This is shown by the spatial coincidence between the molecular outflow and the dust (1.3 mm continuum) and HC₃N emission: both tracers show structures associated to the edges of the outflow lobes. Basically, the global picture sketched for the Class 0 object L1157-mm by Gueth et al. ([CITE]) is supported. We find possible evidence of infall, but we do not detect any velocity gradient indicative of a rotating circumstellar disk.