63 μm jets in class 0 sources detected by herschel

Abstract

We present Herschel PACS mapping observations of the [O i] 63 μm line toward protostellar outflows in the L1448, NGC 1333-IRAS4, HH 46, BHR 71, and VLA 1623 star-forming regions. We detect emission spatially resolved along the outflow direction, which can be associated with a low-excitation atomic jet. In the L1448-C, HH 46 IRS, and BHR 71 IRS1 outflows this emission is kinematically resolved into blue- and redshifted jet lobes, having radial velocities up to 200 km s-1. In the L1448-C atomic jet the velocity increases with the distance from the protostar, similarly to what is observed in the SiO jet associated with this source. This suggests that [O i] and molecular gas are kinematically connected and that the latter could represent the colder cocoon of a jet at higher excitation. Mass flux rates ((O i)) have been measured from the [O i] 63 μm luminosity adopting two independent methods. We find values in the range (1-4) X 10-7 yr-1 for all sources except HH 46, for which an order of magnitude higher value is estimated. (O i) are compared with mass accretion rates (acc) onto the protostar and with derived from ground-based CO observations. (O i)/acc ratios are in the range 0.05-0.5, similar to the values for more evolved sources. (O i) in HH 46 IRS and IRAS4A are comparable to (CO), while those of the remaining sources are significantly lower than the corresponding (CO). We speculate that for these three sources most of the mass flux is carried out by a molecular jet, while the warm atomic gas does not significantly contribute to the dynamics of the system.