YSO jets in the Galactic plane from UWISH2 – II. Outflow luminosity and length distributions in Serpens and Aquila

ABSTRACT

Jets and outflows accompany the mass accretion process in protostars and young stellar objects. Using a large and unbiased sample, they can be used to study statistically the local feedback they provide and the typical mass accretion history. Here we analyse such a sample of molecular hydrogen emission-line objects in the Serpens and Aquila part of the Galactic plane. Distances are measured by foreground star counts with an accuracy of 25 per cent. The resulting spacial distribution and outflow luminosities indicate that our objects sample the formation of intermediate-mass objects. The outflows are unable to provide a sizeable fraction of energy and momentum to support, even locally, the turbulence levels in their surrounding molecular clouds. The fraction of parsec scale flows is one quarter and the typical dynamical jet age of the order of 10⁴ yr. Groups of emission knots are ejected every 10³ yr. This might indicate that low-level accretion rate fluctuations and not FU-Ori-type events are responsible for the episodic ejection of material. Better observational estimates of the FU-Ori duty cycle are needed.