Confronting the Outflow-Regulated Cluster Formation Model With Observations

Abstract

Protostellar outflows have been shown theoretically to be capable of maintaining supersonic turbulence in cluster-forming clumps and keeping the star formation rate per free-fall time as low as a few percent. We aim to test two basic predictions of this outflow-regulated cluster formation model, namely (1) the clump should be close to virial equilibrium and (2) the turbulence dissipation rate should be balanced by the outflow momentum injection rate, using recent outflow surveys toward 8 nearby cluster-forming clumps (B59, L1551, L1641N, Serpens Main Cloud, Serpens South, ρ Oph, IC 348, and NGC 1333). We find, for almost all sources, that the clumps are close to virial equilibrium and the outflow momentum injection rate exceeds the turbulence momentum dissipation rate. In addition, the outflow kinetic energy is significantly smaller than the clump gravitational energy for intermediate and massive clumps with M cl a few × 10 2 M ⊙ , suggesting that the outflow feedback is not enough to disperse the clump as a whole. The number of observed protostars also indicates that the star formation rate per free-fall time is as small as a few percent for all clumps. These observationally-based results strengthen the case for outflow-regulated cluster formation.

The JCMT Gould Belt Survey: Understanding the influence of outflows on Gould Belt clouds

“…Contrary to Nakamura & Li (2014), our results suggest the majority of our regions have low virial parameters and low outflow momentum injection-to-dissipation rates for L1688, IC348 and Serpens Main. Our dissimilar findings may be the result of using longer outflow timescales (i.e., Class I age instead of dynamical timescales).…”

“…In the outflow-regulated cluster formation scenario, past work (e.g., Nakamura & Li 2014) suggested (1) the turbulence momentum dissipation rate must balance the outflow momentum injection rate and (2) the region must be close to virial equilibrium. To test this, Nakamura & Li (2014) used line emission from CO isotopologues, where 12 CO J = 3 → 2 and 1 → 0 were used to trace outflow properties and 13 CO J = 1 → 0, C 18 O and N2H + J = 1 → 0 were used to trace ambient properties in regions that partially overlap with our analysis (B59, L1551, L1641N, Serpens Main, Serpens South, L1688, IC 348 and NGC 1333). Their study finds virial parameters close to unity, except in Serpens South and L1688.…”

Thermal balance and comparison of gas and dust properties of dense clumps in the Hi-GAL survey

“…BGPS sources, dominant in the sample, have the same behaviour of the overall trend along with RMS sources for L/M > 1, while the ATLASGAL sources, with lower spectral resolution, show a similar increasing trend but shifted toward larger values of ∆VNT. It is likely that the increasing trend observed for nonthermal velocity dispersion with increasing L/M is due to different feedback processes that appear in more evolved protostellar and young stellar objects and that provide turbulence to the clumps, such as jets and molecular outflows (Federrath et al 2014;Nakamura & Li 2014) and radiation pressure-driven instabilities (Krumholz & Thompson 2012).…”

NGC 3105: A Young Cluster in the Outer Galaxy∗ †

“…Feedback is also a potential regulator of star formation during embedded phases (e.g. Nakamura & Li 2014), and may trigger star formation in surrounding areas (e.g. Bik et al 2014;Getman et al 2014).…”