Baryonic Effects on Lagrangian Clustering and Angular Momentum Reconstruction

TL;DR

This study demonstrates that baryonic components in galaxy-halo systems reliably trace initial angular momenta, and their late-time angular momenta can be reconstructed from initial conditions, aiding cosmological parameter estimation.

Contribution

It shows that baryonic angular momenta are good tracers of initial conditions and can be reconstructed, despite complex baryonic effects, using high-resolution hydrodynamic simulations.

Findings

Baryonic components have similar protoshapes and spin correlations as dark matter.

Baryonic angular momenta can be reconstructed from initial perturbations.

Strong spin correlations persist despite nonlinear evolution and baryonic effects.

Abstract

Recent studies illustrate the correlation between the angular momenta of cosmic structures and their Lagrangian properties. However, only baryons are observable and it is unclear whether they reliably trace the cosmic angular momenta. We study the Lagrangian mass distribution, spin correlation, and predictability of dark matter, gas, and stellar components of galaxy-halo systems using IllustrisTNG, and show that the primordial segregations between components are typically small. Their protoshapes are also similar in terms of the statistics of moment of inertia tensors. Under the common gravitational potential they are expected to exert the same tidal torque and the strong spin correlations are not destroyed by the nonlinear evolution and complicated baryonic effects, as confirmed by the high-resolution hydrodynamic simulations. We further show that their late-time angular momenta traced by total gas, stars, or the central galaxies, can be reliably reconstructed by the initial perturbations. These results suggest that baryonic angular momenta can potentially be used in reconstructing the parameters and models related to the initial perturbations.