Impact of Baryonic Physics on Intrinsic Alignments

TL;DR

This study investigates how assumptions in subgrid models of star formation and feedback affect galaxy intrinsic alignments in cosmological simulations, finding that most statistical measures are robust to these modeling details.

Contribution

The paper demonstrates the robustness of intrinsic alignment statistics to subgrid physics variations and highlights the importance of galactic wind angular momentum in galaxy orientation.

Findings

Statistical measures of intrinsic alignments are largely insensitive to subgrid physics details.

Distribution of misalignment angles is most sensitive to modeling assumptions.

Results align with findings from the EAGLE simulation study.

Abstract

We explore the effects of specific assumptions in the subgrid models of star formation and stellar and AGN feedback on intrinsic alignments of galaxies in cosmological simulations of "MassiveBlack-II" family. Using smaller volume simulations, we explored the parameter space of the subgrid star formation and feedback model and found remarkable robustness of the observable statistical measures to the details of subgrid physics. The one observational probe most sensitive to modeling details is the distribution of misalignment angles. We hypothesize that the amount of angular momentum carried away by the galactic wind is the primary physical quantity that controls the orientation of the stellar distribution. Our results are also consistent with a similar study by the EAGLE simulation team.