Massive outflows associated with ATLASGAL clumps

Abstract

We have undertaken the largest survey for outflows within the Galactic plane using simultaneously observed 13COand C18O data. Out of a total of 919 ATLASGAL clumps, 325 have data suitable to identify outflows, and 225(69% ± 3%) show high-velocity outflows. The clumps with detected outflows show significantly higher clumpmasses (Mclump), bolometric luminosities (Lbol), luminosity-to-mass ratios (Lbol Mclump), and peak H2 columndensities (NH2) compared to those without outflows. Outflow activity has been detected within the youngestquiescent clump (i.e., 70 mm weak) in this sample, and we find that the outflow detection rate increases withMclump, Lbol, Lbol Mclump, and NH2, approaching 90% in some cases (UC H II regions=93% ± 3%;masers=86% ± 4%; HC H II regions=100%). This high detection rate suggests that outflows are ubiquitousphenomena of massive star formation (MSF). The mean outflow mass entrainment rate implies a mean accretionrate of ∼ - -10 M⊙ yr 4 1, in full agreement with the accretion rate predicted by theoretical models of MSF. Outflowproperties are tightly correlated with Mclump, Lbol, and Lbol Mclump and show the strongest relation with thebolometric clump luminosity. This suggests that outflows might be driven by the most massive and luminoussource within the clump. The correlations are similar for both low-mass and high-mass outflows over 7 orders ofmagnitude, indicating that they may share a similar outflow mechanism. Outflow energy is comparable to theturbulent energy within the clump; however, we find no evidence that outflows increase the level of clumpturbulence as the clumps evolve. This implies that the origin of turbulence within clumps is fixed before the onsetof star formation.