Bridging the scales of star formation regulation – BRIDGES

Galaxies are factories in which gas gravitationally collapse to form stars. This process is very inefficient: the gas-to-star conversion timescale is ~200 times smaller than the free-fall time. The origin of this inefficiency is one of the main open questions in the field of galaxy evolution. In particular, a novel scenario competes with the usual picture of regulation of star formation by feedback, which is a transition between:
- z~0 : regulation of star formation by small scales (stellar feedback)
- z~2 (10 Gyrs back) : regulation of star formation by large scales (disk dynamics and accretion)_x0003_
If this transition exists, it should leave chemo-dynamical footprints on stars observed today: the processes dominating this regulation impose different star formation law scalings with the galaxy environment and more than half of the stars in the local Universe formed during the peak of cosmic star formation, at 1<z<3. We thus need to understand the difference in star formation regulation between z~0 and z~2 galaxies.<br />The key is thus to understand the balance and interactions between the following processes: disk dynamics, gas accretion and star formation feedback. The challenge is to probe the coupling between the scales of accretion and disk dynamics (10s of kpc) and that of the structuration of the interstellar medium (ISM), that is the sonic scale (0.1 pc).
For this purpose, I developed a novel numerical method able to couple those scales for idealised disk simulations: an encapsulated zoom that allows to self-consistently simulate a kpc-sized star-forming region at 0.1 pc resolution, along with its galactic background. This method will be used together with shearing boxes and idealized disks to understand energy injections of these processes, their cascade, their impact on the structuration of the ISM and on star formation.