Massive Galaxies at High-z: Assembly Patterns, Structure & Dynamics in the Fast Phase of Galaxy Formation

TL;DR

This study uses hydrodynamical simulations to analyze the assembly, structure, and dynamics of massive galaxies at high redshifts (z=4-6), revealing their adherence to fundamental scaling relations and the origin of observed tilts in their dynamical planes.

Contribution

It demonstrates that massive high-z galaxies follow specific scaling relations and introduces the concept of tilted fundamental planes at galactic scales based on simulation data.

Findings

Massive galaxies at high z follow scaling relations defining virial and dynamical planes.

Galaxies at high z lie on fundamental planes, with tilts explained by physical processes.

Differences in gas heating behavior influence galaxy formation at high redshift.

Abstract

Relaxed, massive galactic objects have been identified at redshifts z = 4;5; and 6 in hydrodynamical simulations run in a large cosmological volume. This allowed us to analyze the assembly patterns of the high mass end of the galaxy distribution at these high zs, by focusing on their structural and dynamical properties. Our simulations indicate that massive objects at high redshift already follow certain scaling relations. These relations define virial planes at the halo scale, whereas at the galactic scale they define intrinsic dynamical planes that are, however, tilted relative to the virial plane. Therefore, we predict that massive galaxies must lie on fundamental planes from their formation. We briefly discuss the physical origin of the tilt in terms the physical processes underlying massive galaxy formation at high z, in the context of a two-phase galaxy formation scenario. Specifically, we have found that it lies on the different behavior of the gravitationally heated gas as compared with cold gas previously involved in caustic formation, and the mass dependence of the energy available to heat the gas.