On the Size Evolution of a Galactic Disk in Hierarchical Merging of Cold Dark Matter Halos

TL;DR

This paper explores how dark matter subhalos influence the size and evolution of galactic disks over cosmic time, using semi-analytic models aligned with numerical simulations.

Contribution

It introduces a method to estimate the maximum size of galactic disks based on subhalo orbital properties, linking dark matter interactions to observable disk characteristics.

Findings

Massive disks can be larger due to stability against subhalo destruction.

Disk size at low redshift can exceed that at high redshift for the same mass.

Dark matter substructures dynamically limit galactic disk formation and growth.

Abstract

We investigate the dynamical effects of dark matter subhalos on the structure and evolution of a galactic disk, using semi-analytic method that includes approximated and empirical relations as achieved in detailed numerical simulations of the cold dark matter model. We calculate the upper limit for the size of a galactic disk at a specific redshift $z$, based on the orbital properties of subhalos characterized by their pericentric distances from the center of a host halo. We find that this possibly largest size of a disk as determined by the smallest pericentric distances of subhalos shows the characteristic properties, which are basically in agreement with an observed galactic disk at low and high $z$. Namely, it is found that a massive disk can have a larger size than a less massive one, because of its stability against the destruction effect of subhalos. Also, with fixed mass, the size of a galactic disk at low $z$ can be larger than that at high $z$, reflecting the orbital evolution of subhalos with respect to a host halo. These results suggest that the presence and structure of a galactic disk may be dynamically limited by the interaction with dark matter substructures, especially at high $z$.