20210819 - Enrique Vázquez-Semadeni
Channel: Coloquio IRyA
Date: 2021-08-21

Speaker info: Dr. Enrique Vázquez-Semadeni, IRyA
https://www.irya.unam.mx/web/en/people/research-staff/e-vazquez


Title: The crucial role of accretion in Global Hierarchical Collapse Flow
Abstract:
Recent observational and numerical evidence suggests that accretion in the process of star formation occurs not only in the final step, from core to star, but rather at all scales involved. Furthermore, the accretion at each level has a number of unexpected and crucial consequences, which I will discuss in this talk. At the scale of the parent cloud, accretion from its surrounding (possibly atomic) medium counteracts the mass consumption by star formation, maintaining the instantaneously-measured star formation efficiency low. Moreover, it causes an increase in the cloud's mass, density, and radius, causing an evolution from a low- to a high-mass star-forming stage. At the filament level, it allows the establishment of a possibly near-stationary regime in which the filaments act as "rivers", funneling material from the cloud to the core scale. At the core scale, the accretion compresses the innermost regions, driving them to collapse even if they are not Jeans unstable. Finally, the gravity-driven mass transfer rate across the core depends on the core's radial density profile. If the density profile is shallower than r^-2, the cores are capable of accumulating mass without transferring it entirely to their central parts, and thus grow in mass and density. Therefore, accretion is one of the main drivers of evolution in star-forming structures.