Multiple shocks around the low-luminosity protostar IRAS 16293-2422^*

¹ Observatoire de Bordeaux, BP 89, 33270 Floirac, France
² Laboratoire d'Astrophysique, Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 09, France
³ Instituto de Astronomía, UNAM, Apdo Postal 72-3 (Xangari), 58089 Morelia, Michoacán, México
⁴ CESR CNRS-UPS, BP 4346, 31028 Toulouse Cedex 04, France

Corresponding author: A. Castets, Alain.castets@observ.u-bordeaux.fr

Received: 1 February 2001
Accepted: 2 May 2001

Abstract

Using the IRAM 30 m and SEST 15 m telescopes we mapped an area covering 300´´ 220´´around IRAS 16293-2422 in the N₂H⁺ , H₂CO , SiO and molecular transitions. Five positions were also observed in the FIR, between 45 μm and 200 μm, with the Long Wavelength Spectrometer on board ISO, revealing only [C ii] 158 μm and [O i] 63 μm emission. All these observations are used to reconstruct the complex morphology of the region, in which several outflows from several sources co-exist. The N₂H⁺ line emission is strong and centered on 16293E, a recently discovered low mass and very young protostar situated South-East of IRAS 16293-2422. Only weaker N₂H⁺ line emission is associated with the binary system IRAS 16293-2422, presumably because the gas surrounding it is warmer. In addition to the previously known North-East-South-West outflow powered by IRAS 16293-2422, we suggest the existence of a second outflow in this binary system. We also report the discovery of a North-West-South-East flow driven by 16293E. The impact of the outflows with the ambient cloud is probed by the SiO and H₂CO maps, which reveal the presence of at least four, possibly six shocked regions. We discuss in some detail the nature of the shocks, deriving densities, temperatures and column densities of the shocked gas of the various observed components. We suggest that the wind and ambient shocks are probed by the high and low velocity components observed in the SiO lines. The morphology of the H₂CO, SiO and [O i] line emissions are rather different, showing almost all kind of combinations. We discuss the origin of these differences in terms of the age of the shocks, the pre-shock densities and of the composition of the ices which are partially desorbed by the shocks.