An ALMA study of outflow parameters of protoclusters: outflow feedback to maintain the turbulence

With the aim of understanding the role of outflows in star formation, we performed a statistical study of the physical parameters of outflows in 11 massive protoclusters associated with ultracompact H II regions. A total of 106 outflow lobes are identified in these protoclusters using the ALMA CO (3-2), HCN (4-3), and Har (4-3) line observations. Although the position angles of outflow lobes do not differ in these three tracers, HCN and HCO+ tend to detect lower terminal velocity of the identified outflows compared to CO. The majority of the outflows in our targets are young with typical dynamical time-scales of 10(2)-10(4) yr, and are mostly composed of low-mass outflows along with at least one high-mass outflow in each target. An anticorrelation of outflow rate with dynamical time-scale indicates that the outflow rate possibly decreases with time. Also, a rising trend of dynamical time-scale with the mass of the associated core hints that the massive cores might have longer accretion histories than the low-mass cores. Estimation of different energies in these protoclusters shows that outflows studied here cannot account for the generation of the observed turbulence, but can sustain the turbulence at the current epoch as the energy injection rate from the outflows is similar to the estimated dissipation rate.

Automated summary

Through a statistical study of outflows in 11 massive protoclusters, this research finds that the outflows mainly consist of low-mass outflows with at least one high-mass outflow in each target, and suggests a possible decrease in outflow rate over time. Additionally, the study reveals that massive cores may have longer accretion histories.