The Origin of Massive Stars and the Inertial-Inflow Scenario

Padoan et al. 2020, ApJ 900, 82

In the inertial-inflow model, stars are fed by mass inflows that are not driven primarily by gravity, as they are an intrinsic feature of supersonic turbulence. The scenario is inspired by the IMF model of Padoan & Nordlund (Padoan and Nordlund 2002, ApJ 576, 870), where prestellar cores are formed by shocks in converging flows. The characteristic time of the compression is the turnover time of the turbulence on a given scale, which is generally larger than the free-fall time in the post-shock gas, so a pre- stellar core may collapse into a protostar well before the full stellar mass reservoir has reached the core (Padoan & Nordlund 2011, ApJ 741, L22). Only low-mass stars are nearly fully formed after the collapse of the prestellar core (Pelkonen, Padoan et al. 2021, A&A 694, 327), unlike in the core-collapse model. After the initial collapse, the star can continue to grow, as the converging flows that were feeding the prestellar core continue to feed the star, through the mediation of a disk. Thus, the stellar mass reservoir can extend over a turbulent and unbound region much larger than the prestellar core. The name "Inertial-Inflow" refers to the fact that converging flows occur spontaneously in supersonic turbulence and can assemble the stellar mass without relying on a global collapse or on the gravity of the growing star.