2015ApJ...801..121N

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. 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 ({dot}M_jet(O i)) have been measured from the [O i] 63 µm luminosity adopting two independent methods. We find values in the range (1-4)x10^–7 M_☉/ yr for all sources except HH 46, for which an order of magnitude higher value is estimated. {dot}M_jet(O i) are compared with mass accretion rates ({dot}M_acc) onto the protostar and with {dot}M_jet derived from ground-based CO observations. {dot}M_jet(O i)/{dot}M_acc ratios are in the range 0.05-0.5, similar to the values for more evolved sources. {dot}M_jet(O i) in HH 46 IRS and IRAS4A are comparable to {dot}M_jet(CO), while those of the remaining sources are significantly lower than the corresponding {dot}M_jet(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.